Butadiene polymers and process for producing conjugated diene polymers

ABSTRACT

A butadiene polymer (i) having a cis bond unit content of at least 50% based on the total butadiene units, a number average molecular weight (Mn) of 1,000 to 10,000,000, and at least 80%, based on the total molecular chains, of living chains containing a transition metal of group IV of the Periodic table at a terminal thereof; a polymer (ii) obtained by modifying terminals of the polymer (i); and a polymer (iii) obtained by coupling the polymers (i). These polymers (i), (ii) and (iii) are obtained by polymerizing a conjugated diene monomer alone or with a copolymerizable monomer at a specific temperature in the presence of a catalyst comprising a compound (A) of a transition metal of group IV of the periodic table having a cyclopentadienyl structure and a co-catalyst (B) selected from organoaluminum-oxy compound (a) and others and optionally further by contacting the resultant polymer with a terminal modifier or a coupling agent.

TECHNICAL FIELD

This invention relates to a butadiene polymer having a high cis-bondunit content and a high living chain content, and a process forproducing a conjugated diene polymer using a specific metallocenecatalyst.

BACKGROUND ART

Metallocene catalsts generally have a high catalytic activity, andtherefore, they exhibit a high efficiency for production of polymers andgive polymers with well controlled stereoregularity. Further, an attemptof using a metallocene catalyst for the production of rubbers is beingmade.

Polymerization of butadiene using a cyclopentadienyltitaniumtrichloride/methylaluminoxane catalyst was proposed in Macromol. Chem.Rapid. Commun., 1990, vol. 11, p519; J. Organomet. Chem., 1993, vol.451, p67; Macromol. Symp., 1995, vol. 89, p383; and Macromol. RapidCommun., 1996, vol. 17, p781. This polymerization proceeds with a highactivity to give a polymer having a cis-bond unit content of about 80%.However, the polymer is gel-like, and molecular weight, molecular weightdistribution, control of a branched structure and living property of thepolymer are not described in these references. Further, these referencesare silent on an introduction of a functional group in activatedmolecule terminals (hereinafter referred to “terminal modification”),and a reaction of activated molecule terminals with a reactive reagent(hereinafter referred to “coupling-agent”) to give a polymer with ahigher molecular weight (hereinafter referred to “coupling”). Morespecifically polymerization of butadiene using a catalyst prepared bypreviously contacting cyclopentadienyltitanium trichloride withmethylaluminoxane is described in the above cited in Macromol. Chem.Rapid. Commun., 1990, vol. 11, p519, but polymerization conditions andeffects thereof are not described.

Japanese Unexamined Patent Publication (hereinafter abbreviated to“JP-A”) No. H8-113610 discloses polymerization of butadiene using acyclopentadienyltitanium trichloride/methylaluminoxane/triethylaluminumcatalyst to give a butadiene polymer having an Mw/Mn of 1.93. However,control of the branched polymer structure, living property ofpolymerization, and terminal modification and coupling of the polymerare not described.

JP-A H9-77818 discloses a catalyst for polymerization of a conjugateddiene, comprising a combination of a transition metal compound,represented by the following formula (1), of group IV of the periodictable with an aluminoxane, which has a high activity and gives a polymerhaving controlled stereoregularity. It is described in this patentpublication that, when butadiene is polymerized with this catalyst, apolymer having a cis-bond unit content of 96% was obtained. However,this patent publication is silent on molecular weight of the polymer,molecular weight distribution thereof, control of the branched polymerstructure, living property of polymerization, and terminal modificationand coupling of the polymer.

wherein M is a transition metal of group IV of the periodic table, X ishydrogen, a halogen, a C1-12 hydrocarbon group or a C1-12hydrocarbon-oxy group, Y is a C1-20 hydrocarbon group which may form aring together with the cyclopentadienyl group, Z is hydrogen or a C1-12hydrocarbon group, and the pentagon with a circle therein represents acyclopentadienyl ring structure (which is the same in the formula (3)below).

A metallocene catalyst comprising a transition metal compound of groupIV of the periodic table, represented by the following formula (2):

MeO(CO)CH₂CpTiCl₃  (2)

wherein Me is a methyl group and Cp is a cyclopentadienyl ring structure(which is the same in the following chemical formulae), is described inMacromol. Chem., Macromol. Symp., 1997, vol. 118, p55-60. However,polymerization of a conjugated diene using this metallocene catalyst isnot described therein.

Recently, it has been proposed to use the metallocene catalystcomprising the transition metal compound of group IV of the periodictable represented by the formula (2) for polymerization of butadiene inPreprint of the First Symposium on Technology for Novel High-FunctionalMaterials; Industrial Science and Technology Frontier Program, Dec. 10,1997, p77 (Japan). It is described that this polymerization proceededwith a high activity, and the resulting polybutadiene had a highcis-bond unit content and a molecular weight distribution somewhatnarrower than the conventional high-cis butadiene polymers. However,control of the branched polymer structure, living property ofpolymerization, and terminal modification and coupling of the polymerare not described.

Butadiene polymers having a high molecular weight and at least 90% of acis-bond unit content, prepared by using a typical coordinatepolymerization catalyst containing cobalt, nickel, titanium orneodymium, are known. These butadiene polymers have a broad molecularweight distribution, and a large proportion of branched structures. Evena butadiene polymer having the smallest proportion of branchedstructure, prepared by using a neodymium-containing coordinatepolymerization catalyst, satisfies the relationship between theroot-mean-square radius (RMSR, nm) and the absolute molecular weight(MW, g/mol), represented by the following equation:

log(RMSR)=0.638×log(MW)−2.01

As for the butadiene polymers prepared by using a cobalt, nickel ortitanium-containing coordinate catalyst, living property ofpolymerization, and terminal modification and coupling of the polymersare not known. As for the butadiene polymers prepared by using aneodymium-containing coordinate catalyst, it is known that thepolymerization reaction is relatively living, but the content of livingchains is not clear. It is presumed from WO 95/04090 that the maximumvalue of the content of living chains in the polymers with neodymiumcatalyst is 75%. However, as mentioned above, the polymers have a largeproportion of branched structures and a broad molecular weightdistribution, i.e., Mw/Mn of 3.1 or larger.

A process for producing a conjugated diene polymer by polymerizationusing a neodymium-containing coordinate catalyst followed by coupling isknown (for example, JP-A S63-178102, JP-A S63-297403, JP-A S63-305101).However, the polymer before the coupling is presumed as having a broadmolecular weight distribution, namely, Mw/Mn of at least about 3, fromthe GPC eluation curve. This polymer has a large proportion of branchedstructures and the degree of coupling is not clear.

With an organolithium catalyst, living polymerization of butadieneproceeds, and results in a terminal-modified polymer or a coupledpolymer, which have a high molecular weight and a narrow molecularweight distribution, and are substantially free from a branchedstructure. But, the cis-bond unit content of the polymer is not morethan 40%.

To sum up, according to the conventional techniques, it was impossibleto produce a conjugated diene polymer by a stereospecifically highlyactive living polymerization procedure, and also to obtain a conjugateddiene polymer having a high molecular weight and a narrow molecularweight distribution, and substantially not having a branched structure,and having a high cis-bond unit content. It was also impossible toproduce a butadiene polymer by a stereospecifically (i.e., in a mannerby which a polymer with a high cis-bond unit content is obtained) highlyactive living polymerization procedure and to introduce a functionalgroup to a molecule chain terminal or effect coupling.

DISCLOSURE OF THE INVENTION

In view of the foregoing, an object of the present invention is toprovide a butadiene polymer having a high living chain content and ahigh 1,4-cis-bond unit content, and substantially not having a branchedstructure.

Another object of the present invention is to provide a process forproducing a conjugated diene polymer wherein a high living property ofpolymerization is attainable by controlling a polymerizationtemperature.

Still other objects of the present invention are to provide a butadienepolymer having a high cis-bond unit content, a narrow molecular weightdistribution and a high degree of terminal modification, and to providea process for producing a conjugated diene polymer by effectingpolymerization using a specific metallocene catalyst, from which polymera terminal-modified polymer is efficiently obtained by contacting thepolymer with a reactive reagent.

Further objects of the present invention are to provide a coupledbutadiene polymer having a high 1,4-cis-bond unit content and a narrowmolecular weight distribution, and to provide a process for producing aconjugated diene polymer by effecting polymerization using a specificmetallocene catalyst, from which polymer a coupled polymer isefficiently obtained by contacting the polymer with a coupling agent.

Thus, in one aspect of the present invention, there is provided abutadiene polymer which is a homopolymer of butadiene or a copolymer ofbutadiene with a monomer copolymerizable therewith, having at least 50%by weight of butadiene units, and characterized in that the content ofbutadiene units having a cis-bond in the total butadiene units is atleast 50%, the number average molecular weight (Mn) is in the range of1,000 to 10,000,000, and the butadiene polymer has at least 80%, basedon the total molecular chains, of living chains containing a transitionmetal of group IV of the periodic table at a terminal thereof.

In another aspect of the present invention, there is provided a processfor producing a conjugated diene polymer, characterized by polymerizinga conjugated diene monomer alone, or at least 50% by weight of aconjugated diene monomer with not more than 50% by weight of a monomercopolymerizable therewith at a temperature of not higher than 10° C. inthe presence of a catalyst comprising (A) a compound of a transitionmetal of group IV of the periodic table having a cyclopentadienylstructural unit which may have a substituent, and (B) at least oneco-catalyst selected from (a) an organoaluminum-oxy compound, (b) anionic compound capable of reacting with the transition metal compound(A) to give a cationic transition metal compound, (c) a Lewis acidcompound capable of reacting with the transition metal compound (A) togive a cationic transition metal compound, and (d) an organometalliccompound having a main element metal of groups I to III of the periodictable.

In still another aspect of the present invention, there is provided aterminal-modified butadiene polymer which is a homopolymer of butadieneor a copolymer of butadiene with a monomer copolymerizable therewith,having at least 50% by weight of butadiene units, and characterized inthat the content of butadiene units having a cis-bond in the totalbutadiene units is at least 50%; the number average molecular weight(Mn) is in the range of 1,000 to 10,000,000; the ratio (Mw/Mn) of weightaverage molecular weight (Mw) to number average molecular weight (Mn) issmaller than 3.0; a relationship represented by the formula:

log(Mw/Mn)<0.162×log(Mw)−0.682

is satisfied between the weight average molecular weight (Mw) and theratio (Mw/Mn); and the butadiene polymer has at least 10%, based on thetotal polymer chains, of polymer chains having a functional group at aterminal thereof.

In a further aspect of the present invention, there is provided aprocess for producing a terminal-modified conjugated diene polymer,characterized by the steps of:

polymerizing a conjugated diene monomer alone, or at least 50% by weightof a conjugated diene monomer with not more than 50% by weight of amonomer copolymerizable therewith in the presence of a catalystcomprising (A) a compound of a transition metal of group IV of theperiodic table having a cyclopentadienyl structural unit, and (B) atleast one co-catalyst selected from (a) an organoaluminum-oxy compound,(b) an ionic compound capable of reacting with the transition metalcompound (A) to give a cationic transition metal compound, (c) a Lewisacid compound capable of reacting with the transition metal compound (A)to give a cationic transition metal compound, and (d) an organometalliccompound having a main element metal of groups I to III of the periodictable, said transition metal compound (A) being or having been contactedwith said co-catalyst under conditions satisfying the following formulae(α) and (β):

−100<T<80  (α)

0.017<t<6000×exp(−0.0921×T)  (β)

wherein t is contact time (minutes) and T is contact temperature (° C.);and then,

contacting the thus-produced conjugated diene polymer with a reagentcapable of reacting with a living polymer having a transition metal ofgroup IV of the periodic table at a terminal thereof.

In a further aspect of the present invention, there is provided acoupled butadiene polymer composition characterized by comprising:

(I) 0 to 90 parts by weight of a polymer which is a homopolymer ofbutadiene or a copolymer of butadiene with a monomer copolymerizabletherewith, and has at least 50% by weight of butadiene units, and inwhich the content of butadiene units having a cis bond in the totalbutadiene units is at least 50%, the number average molecular weight(Mn) is in the range of 1,000 to 10,000,000, and a relationshiprepresented by the formula:

log(Mw/Mn)<0.162×log(Mw)−0.682

is satisfied between the weight average molecular weight (Mw) and theratio (Mw/Mn); and

(II) 100 to 10 parts by weight of a polymer composed of at least twomolecules of the above-mentioned polymer (I), bonded through a couplingagent.

In a further aspect of the present invention, there is provided aprocess for producing a coupled conjugated diene polymer, characterizedby the steps of:

polymerizing a conjugated diene monomer alone, or at least 50% by weightof a conjugated diene monomer with not more than 50% by weight of amonomer copolymerizable therewith in the presence of a catalystcomprising (A) a compound of a transition metal of group IV of theperiodic table having a cyclopentadienyl structural unit, and (B) atleast one co-catalyst selected from (a) an organoaluminum-oxy compound,(b) an ionic compound capable of reacting with the transition metalcompound (A) to give a cationic transition metal compound, (c) a Lewisacid compound capable of reacting with the transition metal compound (A)to give a cationic transition metal compound, and (d) an organometalliccompound having a main element metal of groups I to III of the periodictable, said transition metal compound (A) being or having been contactedwith said co-catalyst under conditions satisfying the following formulae(α) and (β):

−100<T<80  (α)

0.017<t<6000×exp(−0.0921×T)  (β)

wherein t is contact time (minutes) and T is contact temperature (° C.);and then,

contacting the thus-produced conjugated diene polymer with a couplingagent capable of reacting with a living polymer having a transitionmetal of group IV of the periodic table at a terminal thereof.

BEST MODE FOR CARRYING OUT THE INVENTION Polymerization Catalyst

The catalyst used for polymerization of a conjugated diene in thepresent invention is prepared from (A) a compound of a transition metalof group IV of the periodic table having a cyclopentadienyl structuralunit which may have a substituent, and (B) at least one co-catalystselected from (a) an organoaluminum-oxy compound, (b) an ionic compoundcapable of reacting with the transition metal compound (A) to give acationic transition metal compound, (c) a Lewis acid compound capable ofreacting with the transition metal compound (A) to give a cationictransition metal compound, and (d) an organometallic compound having amain element metal of groups I to III of the periodic table.

Transition Metal Compound (A)

The transition metal compound (A) is a compound of a transition metal ofgroup IV of the periodic table having as a ligand one or morecyclopentadienyl structural units, preferably one cyclopentadienylstructural unit, which may have a substituent. The compound (A) iscalled as a half-metallocene compound or a constrained geometriccatalyst, and is the main constituent of the catalyst used in thepresent invention. The cyclopentadienyl structural unit used hereinbroadly includes not only a cyclopentadienyl structure but also fusedrings formed from a cyclopentadieny structure with another ringstructure, for example, indene structure and fluorene structure. Morespecifically the cyclopentadienyl structure includes those which arerepresent by the following formula (3):

wherein M is a transition metal of group IV of the periodic table, X ishydrogen, a halogen, a C1-12 hydrocarbon group, a C1-12 hydrocarbon-oxygroup, or an amino group which may have a C1-12 hydrocarbon group as asubstituent. Two or more of X may be the same as or different from eachother. X may form a polycyclic structure together with a part of theunsubstituted or substituted cyclopentadienyl structure, through adirect bond or an intervening cross-linking group. p is an integer of 2or 3, and m is an integer of 0 to 5. Q is an organic group, and, when mis an integer of 2 or larger, two or more of Q may be the same as ordifferent from each other. Q may form a polycyclic structure togetherwith a part of the unsubstituted or substituted cyclopentadienylstructure, through a direct bond or an intervening cross-linking group.

The transition metal M of group IV of the periodic table in formula (3)is preferably titanium, zirconium or hafnium. Titanium is mostpreferable.

The halogen as an example of X in formula (3) includes fluorine,chlorine, bromine and iodine atoms. Of these, a chlorine atom is mostpreferable.

The C1-12 hydrocarbon group as an example of X in formula (3) includes,for example, alkyl groups such as methyl and neopentyl, and aralkylgroups having 7 to 12 carbon atoms such as benzyl.

The C1-12 hydrocarbon-oxy group as an example of X in formula (3)includes, for example, alkoxy groups having 1 to 12 carbon atoms such asmethoxy, ethoxy and isopropoxy, and aralkyloxy groups having 7 to 12carbon atoms such as benzyloxy.

The amino group, which may have a C1-12 hydrocarbon group as asubstituent, as an example of X in formula (3) includes, for example,dialkylamino groups having 1 to 12 carbon atoms in each alkyl group,such as dimethylamino, diethylamino, diisopropylamino, dibutylamino anddi-t-butylamino.

When X forms a polycyclic structure together with a part of theunsubstituted or substituted cyclopentadienyl structure through across-linking group, the cross-linking group used includes, for example,hydrocarbon groups having 1 to 14 carbon atoms, such asdimethylmethylene and diphenylmethylene, and silylene groups containinga hydrocarbon group having 1 to 24 carbon atoms, such as methylsilylene,dimethylsilylene, methylphenylsilylene, diphenylsilylene,dibenzylsilylene and tetramethyldisilylene.

As specific examples of the polycyclic structure formed from X which isbonded with a part of the unsubstituted or substituted cyclopentadienylstructure, through a direct bond or an intervening cross-linking group,there can be mentioned an indenyl group and a fluorenyl group.

p, i.e., the number of X in one molecule of the transition metalcompound (A), is an integer of 2 or 3, preferably 3.

As specific examples of the organic group Q, there can be mentionedalkyl groups having 1 to 20 carbon atoms such as methyl, ethyl, propyl,isopropyl, butyl, t-butyl, hexyl, octyl, cyclohexyl and adamantyl; arylgroups having 6 to 20 carbon atoms such as phenyl; aralkyl groups having7 to 30 carbon atoms such as benzyl and triphenylmethyl; hydrocarbongroups containing a silicon atom such as trimethylsilyl; hydrocarbongroups containing a tin atom such as trimethylstannyl; hydrocarbongroups containing a germanium atom such as trimethylgermyl; and groupshaving a Lewis base atomic group with a heteroatom, such as ether,thioether, carbonyl, sulfonyl, ester, thioester, tertiary amino,secondary amino, primary amino, amide, phosphino and phosphinyl.

As specific examples of the polycyclic structure formed from the organicgroup Q which is bonded with a part of the unsubstituted or substitutedcyclopentadienyl structure, through a direct bond or an interveningcross-linking group, there can be mentioned an indenyl group and afluorenyl group.

Among the above-recited examples of the organic group Q, bulkyhydrocarbon groups having 3 to 30 carbon atoms such as trimethylsilyl,t-butyl and triphenylmethyl, and groups having a Lewis base atomic groupwith a heteroatom, are preferable because the polymerization activityand the content of cis-bond unit in polymer are enhanced.

m, i.e., the number of the organic group Q in one molecule of thetransition metal compound (A), is an integer of 0 to 5. m is preferablyat least 1 in view of the high cis-bond unit content in the resultingconjugated diene polymer. When m is at least 2, two or more of theorganic group Q may be the same as or different from each other.

As specific examples of the transition metal compound (A) wherein M istitanium, p is 3 and X is chlorine, there can be mentioned the followingcompounds (1) through (12).

(1) Cyclopentadienyltitanium trichloride wherein m is 0 and which has anunsubstituted cyclopentadienyl group;

(2) Mono-substituted cyclopentadienyltitanium trichloride wherein m is 1and which has a monocyclic substituted cyclopentadienyl group, such asmethylcyclopentadienyltitanium trichloride,trimethylsilylcyclopentadienyltitanium trichloride,t-butylcyclopentadienyltitanium trichloride,triphenylmethylcyclopentadienyltitanium trichloride,adamantylcyclopentadienyltitanium trichloride,(2-methoxyethyl)cyclopentadienyltitanium trichloride (MeOCH₂CH₂CpTiCl₃),[2-(t-butoxy)ethyl]cyclopentadienyltitanium trichloride(t-BuOCH₂CH₂CpTiCl₃; “t-Bu” hereinafter means t-butyl),phenoxyethylcyclopentadienyltitanium trichloride (PhOCH₂CH₂CpTiCl₃; “Ph”hereinafter means phenyl),2-(2-methoxyethoxy)ethylcyclopentadienyltitanium trichloride(MeOCH₂CH₂OCH₂CH₂CpTiCl₃), methoxycarbonylmethylcyclopentadienyltitaniumtrichloride [MeO(CO)CH₂CpTiCl₃],t-butoxycarbonylmethyl-cyclopentadienyltitanium trichloride[t-BuO(CO)CH₂CpTiCl₃], phenoxycarbonylmethyl-cyclopentadienyltitaniumtrichloride, 2-(N,N-dimethylamino)ethylcyclopentadienyltitaniumtrichloride (Me₂NCH₂CH₂CpTiCl₃),2-(N,N-diethylamino)ethyl-cyclopentadienyltitanium trichloride(Et₂NCH₂CH₂CpTiCl₃; “Et” hereinafter means ethyl), and2-(N,N-diisopropylamino)ethyl-cyclopentadienyltitanium trichloride(i-Pr₂NCH₂CH₂CpTiCl₃; “i-Pr” hereinafter means isopropyl);

(3) Di-substituted cyclopentadienyltitanium trichloride wherein m is 2and which has a monocyclic substituted cyclopentadienyl group, such as(1-methyl)(2-trimethylsilyl)cyclopentadienyltitanium trichloride,(1-t-butyl)[3-(2-methoxyethyl)]cyclopentadienyltitanium trichloride,(1-trimethylsilyl)(3-methoxycarbonylmethyl)-cyclopentadienyltitaniumtrichloride and(1-phenyl){3-[2-(N,N-diethylamino)ethyl]}cyclopentadienyltitaniumtrichloride;

(4) Tri-substituted cyclopentadienyltitanium trichloride wherein m is 3and which has a monocyclic substituted cyclopentadienyl group, such as(1,2-dimethyl)(4-trimethylsilyl)cyclopentadienyltitanium trichloride,(1,2-dimethyl)[4-(2-methoxyethyl)]cyclopentadienyltitanium trichloride,(1,2-dimethyl)[4-methoxycarbonylmethyl)-cyclopentadienyltitaniumtrichloride and(1,2-dimethyl){4-[2-(N,N-diethylamino)ethyl]}cyclopentadienyltitaniumtrichloride;

(5) Tetra-substituted cyclopentadienyltitanium trichloride wherein m is4 and which has a monocyclic substituted cyclopentadienyl group, such as(1,2,3-trimethyl)(4-trimethylsilyl)cyclopentadienyltitanium trichloride,(1,2,4-trimethyl)[3-(2-methoxyethyl)cyclopentadienyltitaniumtrichloride,(1,2,3-trimethyl)(4-methoxycarbonylmethyl)cyclopentadienyltitaniumtrichloride and(1,2,3-trimethyl){4-[2-(N,N-diethylamino)ethyl]}cyclopentadienyltitaniumtrichloride;

(6) Penta-substituted cyclopentadienyltitanium trichloride wherein m is5 and which has a monocyclic substituted cyclopentadienyl group, such aspentamethyl-cyclopentadienyltitanium trichloride,pentaphenyl-cyclopentadienyltitanium trichloride,(tetramethyl)-(trimethylsilyl)cyclopentadienyltitanium trichloride,(tetramethyl)(2-methoxyethyl)cyclopentadienyltitanium trichloride,(tetramethyl)(methoxycarbonylmethyl)-cyclopentadienyltitaniumtrichloride and(tetramethyl)[2-(N,N-diethlamino)ethyl]cyclopentadienyltitaniumtrichloride;

(7) Indenyltitanium trichloride wherein m is 1 and which has asubstituted or unsubstituted indenyl group having no substituent on thecyclopentadiene ring, such as indenyltitanium trichloride and(4-methyl)indenyltitanium trichloride;

(8) Substituted indenyltitanium trichloride wherein m is 2 and which hasa substituent on the cyclopentadiene ring, such as(trimethylsilyl)indenyltitanium trichloride,[1-(2-methoxyethyl)]indenyltitanium trichloride,(2-methoxycarbonylmethyl)indenyltitanium trichloride ,{1-[2-(N,N-diethylamino)ethyl]}indenyltitanium trichloride and(4-methyl)(trimethylsilyl)indenyltitanium trichloride;

(9) Substituted indenyltitanium trichloride wherein m is 3 and which hastwo substituents on the cyclopentadiene ring, such as(1-trimethylsilyl)(3-methyl)indenyltitanium trichloride,[1-(2-methoxyethyl)](3-methyl)indenyltitanium trichloride,(2-methoxycarbonylmethyl)(3-methyl)indenyl-titanium trichloride,{1-[2-(N,N-diethylamino)ethyl]}(3-methyl)indenyltitanium trichloride and(3,4-dimethyl)(1-trimethylsilyl)indenyltitanium trichloride;

(10) Substituted indenyltitanium trichloride wherein m is 4 and whichhas three substituents on the cyclopentadiene ring, such as(1-trimethylsilyl)(2,3-dimethyl)indenyltitanium trichloride,[1-(2-methoxyethyl)](2,3-dimethyl)-indenyltitanium trichloride,(2-methoxycarbonylmethyl)-(1,3-dimethyl)indenyltitanium trichloride,{1-[2-(N,N-diethylamino)ethyl]}(2,3-dimethyl)indenyltitanium trichlorideand (2,3,4-trimethyl)(1-trimethylsilyl)-indenyltitanium trichloride;

(11) Substituted or unsubstituted fluorenyltitanium trichloride whereinm is 2 and which has no substituent on the cyclopentadiene ring, such asfluorenyltitanium trichloride and 2-methylfluorenyltitanium trichloride;

(12) Substituted fluorenyltitanium trichloride wherein m is 3 and whichhas a substituent on the cyclopentadiene ring, such as(9-trimethylsilyl)fluorenyltitanium trichloride,[9-(2-methoxyethyl)]fluorenyltitanium trichloride,(9-methoxycarbonylmethyl)fluorenyltitanium trichloride,{9-[2-(N,N-diethylamino)ethyl]}fluorenyltitanium trichloride and(1-methyl)(9-trimethylsilyl)fluorenyltitanium trichloride.

The transition metal compound (A) further includes, for example, thosewhich have a transition metal other than titanium, those in which a partor the entirety of X is a halogen other than chlorine, those in which apart or the entirety of X is a hydrocarbon group, a hydrocarbon-oxygroup or an amide group, those in which X forms a cyclic structuretogether with the organic group Q, and those in which p is an integer of2.

As specific examples of these transition metal compounds (A), there canbe mentioned the following compounds.

(13) Zirconium- or hafnium-containing compounds corresponding to thetitanium-containing compounds as recited above in (1) through (12).Thezirconium- or hafnium-containing compounds include, for example,cyclopentadienylzirconium trichloride,(trimethylsilyl)-cyclopentadienylzirconium trichloride,(2-methoxyethyl)-indenylhafnium trichloride,(methoxycarbonylmethyl)-fluorenylzirconium trichloride and[2-(N,N-diethylamino)-ethyl]cyclopentadienylzirconium trichloride;

(14) Compounds containing fluorine, bromine or iodine instead of a partor the entirety of the chlorine atoms in the transition metal compoundsas recited above in (1) through (13). The fluorine-, bromine- oriodine-containing compounds include, for example,(trimethylsilyl)cyclopentadienyl-titanium trifluoride,(2-methoxyethyl)cyclopentadienyl-titanium tribromide,(methoxycarbonylmethyl)-cyclopentadienyltitanium triiodide and[2-(N,N-diethylamino)ethyl]cyclopentadienyltitanium triiodide;

(15) Compounds having a hydrocarbon group bonded to the transition metalof group IV of the periodic table instead of a part or the entirety ofthe halogen atoms bonded to the transition metal of group IV of theperiodic table in the compounds as recited above in (1) through (14).The hydrocarbon group-containing compounds include, for example,(trimethylsilyl)cyclopentadienyltitanium trimethyl,(2-methoxyethyl)cyclopentadienyltitanium tribenzyl,(methoxycarbonylmethyl)cyclopentadienyltitanium trimethyl and[2-(N,N-diethylamino)ethyl]cyclopentadienyltitanium trimethyl;

(16) Compounds having a hydrocarbon-oxy group bonded to the transitionmetal M of group IV of the periodic table instead of a part or theentirety of the halogen atoms or hydrocarbon groups, bonded to thetransition metal M of group IV of the periodic table in the compounds asrecited above in (1) through (15). The hydrocarbon-oxy group-containingcompounds include, for example,(trimethylsilyl)cyclopentadienyl-titanium trimethoxide,(2-methoxyethyl)cyclopentadienyl-titanium tributoxide,(methoxycarbonylmethyl)cyclopentadienyl-titanium triethoxide and[2-(N,N-diethylamino)ethyl]-cyclopentadienyltitanium tributoxide;

(17) Compounds having an amide group bonded to the transition metal M ofgroup IV of the periodic table instead of a part or the entirety of thehalogen atoms, hydrocarbon groups or hydrocarbon-oxy groups, bonded tothe transition metal M of group IV of the periodic table in thecompounds as recited above in (1) through (16). The amidegroup-containing compounds include, for example,(trimethylsilyl)cyclopentadienyltitanium trisdimethylamide,(2-methoxyethyl)-cyclopentadienyltitanium trisdiethylamide,(methoxycarbonylmethyl)cyclopentadienyltitanium trisdipropylamide and[2-(N,N-diethylamino)ethyl]-cyclopentadienyltitanium trisdioctylamide;

(18) Compounds having a cyclic structure, which is formed at least oneof X together with the organic group Q through a direct bond or anintervening cross-linking group, instead of X and the organic group Q inthe compounds as recited above in (1) through (17). The compounds havingsuch a cyclic structure include, for example,[t-butyl(dimethylcyclopentadienylsilyl)amide]dichlorotitanium,[t-butyl(dimethylcyclopentadienylsilyl)amide]-dimethyltitanium,[t-butyl(dimethylcyclopentadienylsilyl)amide]-dimethylzirconium and[t-butyl(dimethylfluorenylsilyl)amide]dimethyltitanium; and

(19) Compounds, which are the same as the compounds recited above in (1)through (18), except that p is an integer of 2.

The compounds with p of 2 include, for example, cyclopentadienyltitaniumdichloride, methyl-cyclopentadienyltitanium dichloride,trimethylsilyl-cyclopentadienyltitanium dichloride,t-butyl-cyclopentadienyltitanium dichloride,triphenylmethyl-cyclopentadienyltitanium dichloride,adamantyl-cyclopentadienyltitanium dichloride,(trimethylsilyl)-cyclopentadienyltitanium dimethoxide,(trimethylsilyl)-cyclopentadienyltitanium bisdimethylamide and[t-butyl(dimethyl-cyclopentadienylsilyl)amide]chlorotitanium.

Among the above-recited transition metal compounds of (1) through (19),compounds of (1), (2), (7), (8), (11), (12), and compounds of (13)through (19), which correspond to compounds of (1), (2), (7), (8), (11)and (12), are preferable. Compounds of (1) and (2), and compounds of(13) to (19), corresponding to (1) and (2), are more preferable.Compounds of (2) and compounds of (13) through (17) corresponding to(2), and compounds of (19) corresponding to (2) are far more preferable.Compounds of (2) are most preferable.

Among the transition metal compounds (A), as recited above, those whichhave a substituent containing at least one atomic group selected fromcarbonyl, sulfonyl, ether and thioether groups on the cyclopentadienering are preferable. Such transitional metal compounds preferablyinclude transition metal compounds represented by the following formulae(4) and (5). Those of formula (4) are especially preferable.

In formulae (4) and (5), M is a transition metal of group IV of theperiodic table, and X¹, X² and X³ may be the same or different, and arehydrogen, a halogen, a C1-12 hydrocarbon group or a C1-12hydrocarbon-oxy group. Y¹ is hydrogen or a C1-20 hydrocarbon group, andmay form a cyclic structure together with the cyclopentadienylstructure. Z¹ and Z² are hydrogen or a C1-12 hydrocarbon group, and maybe the same or different. A is oxygen or sulfur, and n is an integer of0 to 5.

In formula (4), R¹ is hydrogen, a C1-12 hydrocarbon group, a C1-12hydrocarbon-oxy group or a C1-12 hydrocarbon-thio group. In formula (5),R² is a C1-12 hydrocarbon group.

The transition metal compounds of formulae (4) and (5) are morepreferably metallocene compounds having as ligand one cyclopentadienylgroup, a cyclopentadienyl group having a substituent such as an alkyl,aryl or cycloalkyl group, or a polycyclic structure formed by bonding acyclopentadienyl group together with a substituent, wherein thecyclopentadienyl group in the ligand has at least one atomic groupselected from a >CO structure, a >C═S structure, a —C—O—C— structure anda —C—S—C— structure in the substituent.

As specific examples of the transition metal compound (A) of formula(4), there can be mentioned MeO(CO)CH₂CpTiCl₃, MeO(CO)CH(Me)CpTiCl₃ and{3-[MeO(CO)CH₂]}(1-Me)CpTiCl₃. As a specific example of the transitionmetal compound (A) of formula (5), there can be mentionedMeOCH₂CH₂CpTiCl₃.

The method by which the transition metal compound (A) is prepared is notparticularly limited. For example, MeO(CO)CH₂CpTiCl₃ of formula (4) isprepared by the method described in Macromol. Symp., 1997, vol. 118,p55-60, and MeOCH₂CH₂CpTiCl₃ of formula (5) is prepared by the methoddescribed in Transition Met. Chem., 1990, vol. 15, p483.

Co-catalyst (B)

Among the co-catalysts (B) used in combination with the above-mentionedcompound (A) of transition metal of group IV of the periodic table, theorganoaluminum-oxy compound (a) preferably includes straight-chain orcyclic polymers represented by the following formula (6), namely,aluminoxane:

 —(—Al(R⁵)O—)_(n)—  (6)

wherein R⁵ is a C1-10 hydrocarbon group which is unsubstituted orsubstituted with a substituent selected from a halogen and an R⁶O group(R⁶ is a C1-12 hydrocarbon group), and n is an integer of at least 5,preferably at least 10, and preferably not larger than 100 and morepreferably not larger than 50.

As specific examples of the C1-10 hydrocarbon group, there can be alkylgroups such as methyl, ethyl, propyl and isobutyl. Of these, a methylgroup is preferable.

Among the co-catalyst (B), the ionic compound (b) capable of reactingwith the transition metal compound (A) to form a cationic transitionmetal compound includes an ionic compound which is formed by bonding anon-coordinating anion with a cation.

As specific examples of the non-coordinating anion, there can bementioned tetra(phenyl)borate, tetra(fluorophenyl) borate,tetrakis(difluorophenyl)borate, tetrakis(trifluorophenyl)borate,tetrakis-(tetrafluorophenyl)borate, tetrakis(pentafluorophenyl) borate,tetrakis(tetrafluoromethylphenyl)borate, tetra(toluyl)borate,tetra(xylyl)borate, triphenyl-pentafluorophenyl borate andtris(pentafluorophenyl)phenyl borate.

As specific examples of the cation, there can be mentioned carboniumcations, oxonium cations, ammonium cations, phosphonium cations andferrocenium cations having a transition metal.

As specific examples of the carbonium cations, there can be mentionedtri-substituted cations such as triphenylcarbonium cation andtri-substituted phenylcarbonium cations. The tri-substitutedphenylcarbonium cations include, for example, tri(methylphenyl)carboniumcation and tri(dimethylphenyl)carbonium cation.

As specific examples of the oxonium cations, there can be mentionedalkyloxonium cations such as hydroxonium cation (OH₃ ⁺) andmethyloxonium cation (CH₃OH₂ ⁺); dialkyloxonium cations such asdimethyloxonium cation [(CH₃)₂OH⁺]; and trialkyloxonium cations such astrimethyloxonium cation [(CH₃)₃O⁺] and triethyloxonium cation[(C₂H₅)₃O⁺].

As specific examples of the ammonium cations, there can be mentionedtrialkylammonium cations such as trimethylammonium cation,triethylammonium cation, tripropylammonium cation and tributylammoniumcation; N,N-dialkylanilinium cations such as N,N-diethylaniliniumcation; and dialkylammonium cations such as di(isopropyl)ammonium cationand dicyclohexylammonium cation.

As specific examples of the phosphonium cations, there can be mentionedtriarylphosphonium cations such as triphenylphosphonium cation,tri(methylphenyl)phosphonium cation and tri(dimethylphenyl)phosphoniumcation.

Of the ionic compounds,triphenylcarbonium-tetra(pentafluorophenyl)borate,N,N-dimethylanilinium-tetra(pentafluorophenyl)borate and1,1′-diemthylferrocenium-tetra(pentafluorophenyl)borate are preferable.

Among the co-catalysts (B), as specific examples of the Lewis acidcompound (c) capable of reacting with the transition metal compound (A)to form a cationic transition metal compound, there can be mentionedtris(pentafluorophenyl)boron, tris(monofluorophenyl)boron,tris(difluorophenyl)boron and triphenylborin.

Among the co-catalysts (B), the organometallic compound (d) having amain element metal of groups I to III of the periodic table includes notonly organometallic compounds in a narrow sense, i.e., compounds of ahydrocarbon with a main element metal of groups I to III of the periodictable, but also organometallic halide compounds having the metal andorganometallic hydride compounds having the metal. As specific examplesof the organometallic compound in a narrow sense, there can be mentionedmethyllithium, butyllithium, phenyllithium, dibutylmagnesium,trimethylaluminum, triethylaluminum, triisobutylaluminum,trihexylaluminum and trioctylaluminum. Of these, a trialkylaluminum ispreferable. As specific examples of the organometallic halide compound,there can be mentioned ethylmagnesium chloride, butylmagnesium chloride,dimethylaluminum chloride, diethylaluminum chloride, sesquiethylaluminumchloride and ethylaluminum dichloride. As specific examples of theorganometallic hydride compound, there can be mentioned diethylaluminumhydride and sesquiethylaluminum hydride.

The above-recited compounds (a) to (d) may be used either alone or incombination as the co-catalyst (B) in the present invention. Of these,(a) alone, (c) alone, a combination of (a) with (d), a combination of(b) with (d) and a combination of (c) with (d) are preferable.

When the transition metal compound (A) is a cyclopentadienyl structurehaving a substituent having at least one atomic group selected from acarbonyl group, a sulfonyl group, an ether group and a thioether group,the co-catalyst (B) is preferably aluminoxane (a) or the ionic compound(d) capable of reacting with the transition metal compound (A) to form acationic transition metal compound. In this case, the ionic compound (d)is preferably an ionic compound of an anion oftetrakis(pentafluorophenyl)borate with a cation selected from an aminecation having an active proton such as (CH₃)₂N(C₆H₅)H⁺, atri-substituted carbonium cation such as (C₆H₅)₃C⁺, a carboran cation, ametal carboran cation and a ferrocenium cation having a transitionmetal.

The polymerization can be carried out in the co-presence of a metalhydride. As specific examples of the metal hydride, there can bementioned NaH, LiH, CaH, LiAlH₄ and NaBH₄.

Supported Catalyst

The transition metal compound (A) and/or the co-catalyst (B) can be usedin a state of being supported by a carrier. The carrier includes thosewhich are composed of inorganic compounds and organic high polymers.

The inorganic compounds preferably include inorganic oxides, inorganicchlorides and inorganic hydroxides, which may contain a minor amount ofa carbonate salt or a sulfate salt. Inorganic oxides such as silica,alumina, magnesia, titania, zirconia and calcia, and inorganic chloridessuch as magnesium chloride are especially preferable. These inorganiccompounds are preferably finely divided porous particles having anaverage particle diameter of 5 to 150 μm and a specific surface area of2 to 800 m²/g. The finely divided porous particles can be used aftermoisture is removed by heat-treating the particles, for example, at atemperature of 100 to 800° C.

The organic high polymers preferably have an aromatic ring, asubstituted aromatic ring or a functional group such as hydroxyl, esteror halogen at side chains. As specific examples of the organic highpolymers, there can be mentioned α-olefin homopolymers having afunctional group which is prepared by chemically modifying α-olefinhomopolymers having, for example, etylene, propylene or butene units;α-olefin copolymers; polymers having units of acrylic acid, methacrylicacid, vinyl chloride, vinyl alcohol, styrene or divinylbenzene; andchemically modified polymers thereof.

The carrier composed of the organic high polymer is usually sphericalparticles having an average particle diameter of 5 to 250 μm.

When the transition metal compound (A) and/or the co-catalyst (B) areused in a state of being supported by a carrier, contamination of apolymerization reactor can be avoided because these ingredients (A)and/or (B) are not deposited on the reactor.

Monomers

Conjugated Diene Monomers

Conjugated diene monomers used in the present invention include, forexample, 1,3-butadiene, 2-methyl-1,3-butadiene,2,3-dimethyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1,3-pentadiene and1,3-hexadiene. Of these conjugated diene monomers, 1,3-butadiene and2-methyl-1,3-butadiene are preferable. 1,3-butadiene is most preferable.These conjugated diene monomers may be used either alone or incombination, but use of 1,3-butadiene alone is most preferable.

Copolymerizable Monomers

As specific examples of the monomers copolymerizable with the conjugateddiene monomers, there can be mentioned aromatic vinyl monomers such asstyrene, o-methylstyrene, p-methylstyrene, m-methylstyrene,2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene,α-methyl-p-methylstyrene, o-chlorostyrene, m-chlorostyrene,p-chlorostyrene, p-bromostyrene, 2-methyl-1,4-dichlorostyrene,2,4-dibromostyrene and vinylnaphthalene; cycloolefins such ascyclopentene and 2-norbornene; non-conjugated dienes such as1,5-hexadiene, 1,6-heptadiene, 1,7-octadiene, dicyclopentadiene and5-ethylidene-2-norbornene; and acrylic acid esters, and methacrylic acidesters such as methyl methacrylate.

Process for Producing Conjugated Diene Polymers

The procedure by which a conjugated diene monomer alone, or acombination of at least 50% by weight of a conjugated diene monomer withnot more than 50% by weight of a copolymerizable monomer is polymerizedis not particularly limited. For example, the following procedures (i)through (vi) can be adopted by using the transition metal compound (A)and at least one of the co-catalyst (B).

(i) Transition metal compound (A) and co-catalyst (B) are previouslycontacted with each other, and, while transition metal compound (A) iskept in contact with co-catalyst (B), a monomer is placed in contactwith transition metal compound (A) and co-catalyst (B) to effectpolymerization.

(ii) Transition metal compound (A) and a monomer are previouslycontacted with each other, and, while transition metal compound (A) iskept in contact with the monomer, co-catalyst (B) is placed in contactwith transition metal compound (A) and the monomer to effectpolymerization.

(iii) Co-catalyst (B) and a monomer are previously contacted with eachother, and, while co-catalyst (B) is kept in contact with the monomer,transition metal compound (A) is placed in contact with co-catalyst (B)and the monomer to effect polymerization.

(iv) Transition metal compound (A) and co-catalyst (B) are mixedtogether, the resultant mixture is contacted with a carrier to bethereby supported by the carrier, the thus prepared catalyst isseparated, and then a monomer is contacted with the catalyst to effectpolymerization.

(v) Transition metal compound (A) and a carrier are contacted with eachother, the resultant compound (A)/carrier is contacted with co-catalyst(B) to prepare a catalyst comprising compound (A) plus co-catalyst (B),supported by the carrier, the thus-prepared catalyst is separated, andthen a monomer is contacted with the catalyst to effect polymerization.

(vi) Co-catalyst (B) and a carrier are contacted with each other, theresultant co-catalyst (B)/carrier is contacted with transition metalcompound (A) to prepare a catalyst comprising compound (A) plusco-catalyst (B), supported by the carrier, the thus-prepared catalyst isseparated, and then a monomer is contacted with the catalyst to effectpolymerization.

Of these procedures, procedures (i), (iv), (v) and (vi) are preferablebecause transition metal compound (A) and co-catalyst (B) are previouslycontacted with each other, and, after a lapse of aging time, a monomeris placed in contacted with the compound (A) and co-catalyst (B) while(A) and (B) are kept in contact with each other, and thus, theefficiency of polymerization initiator and the polymerization activityare enhanced, and the molecular weight distribution of polymer becomesnarrower. Procedure (i) is most preferable. When butadiene ispolymerized by this procedure, a butadiene polymer having a molecularweight distribution of below 3.0 as defined as the ratio (Mw/Mn) ofweight average molecular weight (Mw) to number average molecular weight(Mn) is obtained. The Mw/Mn ratio can be easily lowered to not largerthan 1.6, relatively easily lowered to below 1.5, and even possible toreach a value of not larger than 1.4.

Preferably the transition metal compound (A) and the co-catalyst (B) areaged at a temperature in the range of −100° C. to +80° C., morepreferably −80° C. to +70° C. It is preferable that the followinginequality (I) is satisfied between the aging time t(minutes) and agingtemperature T(° C.) when a=0.017 and b=6,000, more preferably whena=0.083 and b=4,000, and most preferably a=0.17 and b=2,000. The agingtime t(minutes) means the time spanning from the commencement of contactof transition metal compound (A) with co-catalyst (B) to thecommencement of polymerization.

a<t<b×exp(−0.0921×T)  (I)

When the aging temperature is higher than +80° C., the intended agingeffect cannot be obtained. In contrast, when the aging temperature islower than −100° C., the aging is not advantageous from an economicalview point. Any problem does not arise even when the aging is carriedout at a low temperature for a long time while the compound (A) is keptin contact with co-catalyst (B). But, when the aging temperature ishigh, the catalyst is liable to be deactivated, and, when the aging timeis long, polymerization becomes difficult to conduct. In contrast, ashort aging time of shorter than 0.017 minute, i.e., within one second,cannot be actually employed.

The transition metal compound (A) and the co-catalyst (B) may be usedeither in a state of a solution or a slurry. A solution state ispreferable because of high polymerization activity. As specific examplesof a solvent used for the preparation of the solution or slurry, therecan be mentioned hydrocarbons such as butane, pentane, hexane, heptane,octane, cyclohexane, mineral oil, benzene, toluene and xylene; andhalogenated hydrocarbons such as chloroform, methylene chloride,dichloroethane and chlorobenzene. Of these, aromatic hydrocarbons suchas benzene and toluene are preferable. These solvents may be used eitheralone or in combination.

The amount of the catalyst is preferably in the range of 100 to 0.01m-mol, more preferably 10 to 0.1 m-mol, and most preferably 5 to 0.2m-mol, as the amount of transition metal compound (A). Thepolymerization reaction of the present invention carried out at aspecific temperature is a living polymerization as hereinaftermentioned. Therefore, the molecular weight of polymer can be controlledby varying the amount of transition metal compound (A) per unit amountof a monomer. For example, when the amount of transition metal compound(A) is in the range of 5 to 0.2 mols per mol of butadiene, a butadienepolymer having a very narrow molecular weight distribution, i.e., anMw/Mn ratio of not larger than 1.6, preferably below 1.5, can easily beobtained.

The ratio by mol of organoaluminum-oxy compound (a) such as aluminoxaneto the transition metal compound (A) is preferably in the range of 10 to10,000, more preferably 100 to 5,000 and most preferably 200 to 3,000.The ratio by mol of the ionic compound (b) to the transition metalcompound (A) is preferably in the range of 0.01 to 100, and morepreferably 0.1 to 10. The ratio by mol of the Lewis acid compound (c) tothe transition metal compound (A) is preferably in the range of 0.01 to100, and more preferably 0.1 to 10. When an organometallic compound (d)is used, the ratio by mol of the organometallic compound (d) to thetransition metal compound (A) is preferably in the range of 0.1 to10,000, and more preferably 1 to 1,000. The above-mentioned amounts ofco-catalyst (B) apply to the case where the respective ingredient (a),(b), (c) or (d) isusedalone. If two or more of co-catalysts (B) are usedin combination, an appropriate amount thereof varies depending upon theparticular proportion of the co-catalysts used.

The polymerization of a conjugated diene monomer alone or a combinationof a conjugated diene monomer with a copolymerizable monomer can becarried out by a solution polymerization method using an inert solvent,a slurry polymerization method, and a bulk polymerization method whereina monomer functions as a diluent. A vapor phase polymerization methodusing a vapor phase stirring vessel or a vapor phase fluidized bed mayalso be employed. Of these, a solution polymerization method ispreferable because high living polymerization property and a polymerwith a narrow molecular weight distribution are obtained. Any ofbatchwise, semi-batchwise and continuous polymerization methods may beemployed.

The polymerization temperature is not particularly limited, but isusually not higher than 20° C., preferably in the range of −100° C. to+20° C., more preferably −80° C. to +15° C., and most preferably −60° C.to +10° C.

However, when a homopolymer of butadiene or a copolymer of at least 50%by weight of butadiene with not more than 50% by weight of a monomercopolymerizable therewith, characterized in that the content ofbutadiene units having a cis-bond in the total butadiene units is atleast 50%, the number average molecular weight (Mn) is in the range of1,000 to 10,000,000, and the butadiene polymer has at least 80%, basedon the total molecular chains, of living chains containing a transitionmetal of group IV of the periodic table at a terminal thereof, isproduced, the polymerization temperature is not higher than +10° C.,usually in the range of −100° C. to +10° C., preferably −80° C. to +10°C., and more preferably −60° C. to +10° C.

A low polymerization temperature is preferable from a view point suchthat a high living polymerization property is attained to give a polymerhaving a reduced number of branched structure, and the rate ofinitiation reaction relative to the rate of propagation reaction isenhanced to give a polymer having a narrow molecular weightdistribution. But, a too low polymerization temperature is sometimesdifficult to maintain.

The polymerization time is usually in the range of 1 second to 360minutes, and the polymerization pressure is usually in the range ofatmospheric pressure to 30 kg/cm². The inert solvent used may beselected from those recited above, and may be used either alone or as amixture.

A polar compound may be incorporated in the polymerization system, whichincludes, for example, ethers such as ethyl ether, diglyme,tetrahydrofuran and dioxane, and amines such as triethylamine andtetramethylethylenediamine.

A chain transfer agent can be incorporated in the polymerization systemto control the molecular weight of polymer. Chain transfer agents whichare generally used for the production of cis-1,4-polybutadiene rubbercan be used. As preferable examples of the chain transfer agent, therecan be mentioned allenes such as 1,2-butadiene, cyclic dienes such ascyclooctadiene, and hydrogen.

The termination of polymerization can be effected usually byincorporating a polymerization stopper in the polymerization system whenthe desired conversion is reached. The polymerization stopper usedincludes, for example, alcohols such as methanol, ethanol, propanol,butanol and isobutanol. These alcohols may be incorporated with an acidsuch as hydrochloric acid.

By termination of polymerization, the bond between the terminal ofpolymer chain and the transition metal of group IV of the periodic tableis severed, and the polymerization reaction stops. The polymer having atransition metal of group IV of the periodic table bonded at a terminalthereof is called “a living polymer”, and, the polymer from which thetransition metal is severed by the termination of polymerization iscalled “a dead polymer”. By the term “polymer” hereinafter used, we meanboth of the living polymer and the dead polymer.

The procedure of recovering a polymer after the termination ofpolymerization is not particularly limited. For example, asteam-stripping procedure and a procedure of depositing a polymer with apoor solvent can be used.

An antioxidant can be incorporated in a polymer at any step during thecourse spanning from the termination of polymerization to the finaldrying of polymer. Especially when the polymer is heated to atemperature at which the polymer is thermally degraded, for example, ata heat-drying step, an antioxidant is added preferably before thepolymer is heated to that temperature. The antioxidant includes, forexample, phenolic stabilizers, sulfur-containing stabilizers,phosphorus-containing stabilizers and amine stabilizers.

The phenolic stabilizers are described, for example, in JP-A H4-252243.As specific examples of the phenolic stabilizers, there can be mentioned2,6-di-tert.-butyl-4-methylphenol, 2,6-di-tert.-butyl-4-ethylphenol,2,6-di-tert.-butyl-4-butylphenol, 2,6-di-tert.-butyl-4-isobutylphenol,2-tert.-butyl-4,6-dimethylphenol, 2,4,6-tricyclohexylphenol,2,6-di-tert.-butyl-4-methoxylphenol, 2,6-di-phenol-4-octadecyloxyphenol,n-octadecyl-3-(3′,5′-di-tert.-butyl-4-hydroxyphenyl)propionate,tetrakis-[methylene-3-(3′,5′-di-tert.-butyl-4′-hydroxyphenyl)-propionate]-methane,1,3,5-trimethyl-2,4,6-tris(3,5-di-tert.-butyl-4-hydroxybenzyl)benzene,2,4-bis-(octylthiomethyl)-6-methylphenol,2,4-bis(2′,3′-dihydroxypropylthiomethyl)-3,6-dimethylphenol and2,4-bis(2′-acetyloxyethylthiomethyl)-3,6-dimethylphenol.

As specific examples of the sulfur-containing stabilizers, there can bementioned dilauryl thiodipropionate, distearyl thiodipropionate,aminothioglycolate, 1,1-thiobis(2-naphthol), ditridecyl thiodipropionateand distearyl β,β′-thiodipropionate.

The phosphorus-containing stabilizers are also known, and, as specificexamples thereof, there can be mentioned tris(nonylphenyl)phosphite,cyclic neopentanetetraylbis-(octadecylphosphite) andtris(2,4-di-tert.-butylphenyl)-phosphite.

As specific examples of the amine stabilizers, there can be mentionedphenyl-α-naphthylamine, phenyl-β-naphthylamine, aldol-α-naphthylamine,p-isopropoxy-diphenylamine, p-(p-toluenesulfonylamide)diphenylamine,bis(phenylisopropylidene)-4,4′-diphenylamine,N,N′-diphenylethylenediamine, N,N′-diphenylpropylenediamine, octylateddiphenylamine, N,N′-diphenyl-p-phenylenediamine andN-isopropyl-N′-phenyl-p-phenylenediamine.

The amount of the antioxidant is usually in the range of 0.01 to 5.0parts by weight, preferably 0.05 to 2.5 parts by weight, based on 100parts by weight of the conjugated diene polymer. When the amount of theantioxidant is too small, the effect of the antioxidant is notmanifested and the polymer has poor heat-resistance. In contrast, whenthe antioxidant is too large, the conjugated diene polymer exhibits heatdiscoloration. The antioxidant may be used alone or as a combination ofat least two thereof.

Conjugated Diene Polymers

By the process of the present invention a conjugated diene polymer canbe produced efficiently with a high activity. A conjugated diene polymerhaving a desired molecular weight and a narrow molecular weightdistribution can be obtained by carrying out the polymerization at aspecific temperature to effect living polymerization, and usingacatalyst prepared with aging.

The conjugated diene polymer produced by the process of the presentinvention may be either a living polymer or a dead polymer. When thepolymer is a copolymer, the copolymer may be either a random copolymeror a block copolymer.

The butadiene polymer of the invention is one of the above-mentionedconjugated diene polymers, and a living homopolymer of butadiene or aliving copolymer of at least 50% by weight of butadiene with not morethan 50% by weight of a monomer copolymerizable therewith, characterizedin that the content of butadiene units having a cis-bond in the totalbutadiene units is at least 50%, the number average molecular weight(Mn) is in the range of 1,000 to 10,000,000, and the butadiene polymerhas at least 80%, based on the total molecular chains, of living chainscontaining a transition metal of group IV of the periodic table at aterminal thereof.

The living polymerizability is evaluated usually based on the followingfacts: (i) the polymer has a very narrow molecular weight distribution,namely, the polymer is substantially monodisperse, (ii) as the polymeryield is increased with proceeding of polymerization, the number averagemolecular weight (Mn) is increased in proportion but the molecularweight distribution Mw/Mn is not broadened, (iii) the number averagemolecular weight (Mn) of polymer can be controlled by the ratio ofmonomer amount/catalyst amount, (iv) post polymerization (i.e., secondpolymerization) of the living polymer can be effected, and (v) aterminal of the living polymer can be made functional.

The content of living polymer chain can be evaluated by theabove-mentioned facts (i) through (v), and especially by (iv) and (v)with high accuracy.

More specifically, as for the above-mentioned fact (iv), when the livingpolymer is subjected to second polymerization, the content of livingchains can be determined according to the gel permeation chromatography(GPC) curve of the polymer after the second polymerization, namely, bythe mol fraction of molecules forming the peak of the polymer having amolecular weight higher than that of the living polymer measured beforethe second polymerization. For example, if the content of living chainsis at least 80%, the mol fraction of the polymer obtained before thesecond polymerization is smaller than 20%. Thus, the mol fraction ofmolecules forming the peak of the polymer having a molecular weighthigher than that of the living polymer measured before the secondpolymerization is at least 80%. Note, if by-products with a lowmolecular weight are produced, the content of living chains as obtainedby measurement is lower than the true content of living chains becausethe presence of polymers having a molecular weight smaller than that ofthe polymer obtained by the first polymerization.

As for the above-mentioned fact (e), the content of living chains can bedetermined by the degree of terminal modification as measured when aterminal of a living polymer is modified. For example, when the degreeof terminal modification is at least 80%, the content of living chainsis at least 80%. The degree of terminal modification can be calculatedfrom the number average molecular weight Mn of a polymer and theconcentration of terminal group introduced by terminal modification. Thedetermining procedure of the concentration of a terminal group variesdepending upon the particular terminal modifier used. For example, inthe case where a terminal of a living polymer of butadiene is modifiedwith carbon monoxide, Mn is measured by GPC and the content of terminalcarbonyl group is measured by infrared absorption spectroscopy.

The butadiene polymer of the present invention is a homopolymer of1,3-butadiene, or a copolymer comprising at least 50%, preferably atleast 70%, more preferably at least 80% and especially preferably atleast 90%, of recurring units derived from 1,3-butadiene. Mostpreferably the butadiene polymer is a homopolymer of 1,3-butadiene. Whenthe proportion of 1,3-butadiene units in the copolymer is too small, thebenefit of the butadiene polymer of the present invention, attained bythe high content of cis-bond units therein, is reduced.

The content of butadiene units having a cis-bond in the total butadieneunits is at least 50% by weight, preferably at least 70% by weight, morepreferably at least 80% by weight, and especially preferably at least90% by weight. If the content of cis-bond is too small, the tensilestrength is reduced and the properties desired as rubber are lost. Bythe term “cis-bond” herein used, we mean 1,4-cis-bond.

The number average molecular weight Mn of the butadiene polymer of thepresent invention is in the range of 1,000 to 10,000,000, preferably5,000 to 5,000,000, more preferably 10,000 to 2,000,000, and mostpreferably 20,000 to 1,000,000. If the molecular weight is too small,the physical properties including mechanical strength of polymer aredeteriorated. In contrast, if the molecular weight is too large, shapingof polymer becomes difficult.

The ratio of Mw/Mn of the butadiene polymer of the present invention isnot particularly limited, but is preferably not larger than 1.9, morepreferably not larger than 1.6 and most preferably not larger than 1.4.If the ratio of Mw/Mn is too large, the properties including abrasionresistance of a cured product are deteriorated.

The branched structure of polymer is evaluated by the relationship ofthe root mean square radius (hereinafter abbreviated to “RMSR”)determined by measurement of GPC-multi-angle light scattering (MALLS),with the absolute molecular weight (MW). In this measurement,tetrahydrofuran is used as elute and the measurement is conducted at atemperature of 40±2° C. By the term “branched structure” used herein, wemean polymer structures formed by elementary reactions including shiftreaction, other than normal addition reaction, of monomer. It is notmeant a branched-chain vinyl structure derived from 1,2-bond. Thebranched structure of the butadiene polymer of the present invention isnot particularly limited, but preferably satisfies the relationship ofRMSR (nm) with MW (g/mol), represented by the following inequality (II),provided that c=0.638 and d=2.01.

log(RMSR)>c×log(MW)−d  (II)

The butadiene polymer of the present invention is substantially freefrom a branched structure and has a high content of cis-bond units, andincludes the following four types of polymers.

Type 1: A homopolymer of butadiene or a copolymer of at least 50% byweight of butadiene with not more than 50% by weight of a monomercopolymerizable therewith, wherein the content of butadiene units havinga cis-bond in the total butadiene units is at least 50%, andrelationship of Mw with the ratio of Mw/Mn, represented by the followinginequality (III) is satisfied, provided that e=0.162 and f=0.682.

log(Mw/Mn)<e×log(MW)−f  (III)

The relationship of inequality (III) is satisfied preferably providedthat e=0.161, more preferably e=0.160 and especially preferably e=0.159,and preferably provided that f=0.684, more preferably f=0.687, andespecially preferably f=0.690.

Type 2: A homopolymer of butadiene or a copolymer of at least 50% byweight of butadiene with not more than 50% by weight of a monomercopolymerizable therewith, wherein the content of butadiene units havinga cis-bond in the total butadiene units is at least 50%, the ratio(Mw/Mn) of weight average molecular weight (Mw) to number averagemolecular weight (Mn) is not larger than 1.6, preferably smaller than1.5 and more preferably not larger than 1.4, and Mn is in the range of1,000 to 10,000,000.

Type 3: A homopolymer of butadiene or a copolymer of at least 50% byweight of butadiene with not more than 50% by weight of a monomercopolymerizable therewith, wherein the content of butadiene units havinga cis-bond in the total butadiene units is at least 50%, the numberaverage molecular weight (Mn) is in the range of 1,000 to 10,000,000,and the inequality (II) showing the relationship between RMSR (nm) andMW (g/mol) is satisfied at c=0.638 and d<2.01. The inequality (II) issatisfied preferably even at d=2.00 and more preferably d=1.99. Thisbutadiene homopolymer or copolymer is characterized as beingsubstantially free from a branched structure and a high-content ofcis-bond units.

Type 4: A living butadiene polymer or a dead butadiene polymer obtainedby terminating the polymerization reaction of the living butadienepolymer, which is a homopolymer of butadiene or a copolymer of butadienewith a monomer copolymerizable therewith, wherein the content ofbutadiene units having a cis-bond in the total butadiene units is atleast 50%, the number average molecular weight (Mn) is in the range of1,000 to 10,000,000, and the polymer has at least 80%, based on thetotal molecular chains, of living chains containing a transition metalof group IV of the periodic table at a terminal of polymer molecule.

Process for Producing Terminal-Modified Conjugated Diene Polymer

The living conjugated diene polymer of the present invention or theliving conjugated diene polymer produced by the process of the presentinvention has living chains containing a transition metal of group IV ofthe periodic table at a terminal of each polymer molecule. In theprocess for producing a terminal-modified conjugated diene polymer, theliving conjugated diene polymer is contacted with a reagent capable ofreacting with the transition metal-bonded terminal of the living polymerto introduce a functional group, i.e., a terminal modifier, whereby aterminal-modified conjugated diene polymer is produced.

As specific examples of the terminal modifier, there can be mentionedmolecular oxygen, carbon monoxide, carbon dioxide, carbon disulfide,carbonyl sulfide and sulfur dioxide, and the following compounds.

Molecular halogens such as chlorine, bromine and iodine; and organichalides such as vinylbenzyl chloride;

hetero-three-membered ring compounds which include epoxy compounds suchas ethylene oxide, propylene oxide, cyclohexene oxide, styrene oxide,epoxidized soybean oil and epoxidized natural rubber; thiirane compoundssuch as thiirane, methylthiirane and phenylthiirane; and ethyleneimineand derivatives thereof such as N-phenylethyleneimine andN-(β-cyanoethyl)ethyleneimine, and propyleneimine;

ketones which include N-substituted aminoketones such as4-dimethylaminoacetophenone, 4-diethylaminoacetophenone,1,3-bis(diphenylamino)-2-proanone,1,7-bis(methylethylamino)-4-heptanone, 4-dimethylaminobenozophenone,4-di-t-butylaminobenozophenone, 4-diphenylaminobenozophenone,4,4′-bis(dimethylamino)benozophenone,4,4′-bis(diethylamino)benozophenone and4,4′-bis(diphenylamino)benozophenone; and N-substituted aminothioketonessuch as those corresponding to the above-recited N-substitutedaminoketones;

aldehyde compounds which include N-substituted benzaldehydes such as4-dimethylaminobenzaldehydes, 4-diphenylaminobenzaldehydes and4-divinylaminobenzaldehydes; N-substituted benzthioaldehydes such asthose corresponding to the above-recited N-substituted benzaldehydes;ketene compounds such as ethylketene, butylketene, phenylketene andtoluylketene; thioketene compounds such as ethylthioketene,butylthioketene, phenylthioketene and toluylthioketene; ester compoundssuch as ethyl acetate; lactone compounds such as γ-butyrolactone; acidhalide compounds such as propionyl chloride, octanoyl chloride, stearoylchloride, benzoyl chloride, phthaloyl chloride and maleyl chloride;carbodiimide compounds such as N,N′-diphenylcarbodiimide andN,N′-diethylcarbodiimide;

pyridine compounds which include pyridine compounds having a halogen ona carbon atom adjacent to the nitrogen atom, such as2-amino-6-chloropyridine, 2,5-dibromopyridine,4-chloro-2-phenylquinazoline, 2,4,5-tribromoimidazole,3,6-dichloro-4-methylpyridazine, 3,4,5-trichloropyridazine,4-amino-6-chloro-2-mercaptopyrimidine,2-amino-4-chloro-6-methylpyrimidine, 2-amino-4,6-dichloropyrimidine,6-chloro-2,4-dimethoxypyrimidine, 2-chloropyrimidine,2,4-dichloro-6-methylpyrimidine, 4,6-dichloro-2-(methylthio)-pyrimidine,2,4,5,6-tetrachloropyrimidine, 2,4,6-trichloropyrimidine,2-amino-6-chloropyrazine, 2,6-dichloropyrazine,2,4-bis(methylthio)-6-chloro-1,3,5-triazine,2,4,6-trichloro-1,3,5-triazine, 2-bromo-5-nitrothiazole,2-chlorobenzothiazole and 2-chloro-benzoxazole; pyridyl-substitutedketones such as methyl-2-pyridylketone, methyl-4-pyridylketone,propyl-2-pyridylketone, di-4-pyridylketone, propyl-3-pyridylketone and2-benzoylpyridine; and vinylpyridines such as 2-vinylpyridine and4-vinylpyridine;

amide compounds which include N,N-dimethylformamide, acetamide,N,N-diethylacetamide, aminoacetamide,N,N-dimethyl-N′,N′-dimethylaminoacetamide, N,N-dimethylaminoacetamide,N,N-diethylaminoacetamide, N,N-dimethyl-N′-ethylaminoacetamide,acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide,nicotinamide, isonicotinamide, picolinamide,N,N-dimethylisonicotinamide, succinamide, phthalamide,N,N,N′,N′-tetramethylphthalamide, oxamide, N,N,N′,N′-tetramethyloxamide,2-furancarboxylic acid amide, N,N-dimethyl-2-furancarboxylic acid amideand N-ethyl-N-methyl-quinolinecarboxylic acid amide; N-substitutedlactams such as N-methyl-β-propiolactam, N-phenyl-β-propiolactam,N-methyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone,N-phenyl-5-methyl-2-pyrrolidone, N-methyl-2-piperidone,N-phenyl-2-piperidone and N-methyl-ε-caprolactam; and N-substitutedthiolactams such as those corresponding to the above-recitedN-substituted lactams;

urea compounds which include N-substituted cyclic ureas such as1,3-diethyl-2-imidazolydinone, 1,3-dimethyl-2-imidazolydinone,1,1-dipropyl-2-imidazolydinone, 1-methyl-3-ethyl-2-imidazolydinone,1-methyl-3-propyl-2-imidazolydinone, 1-methyl-3-butyl-2-imidazolydinone,1-methyl-3-(2-methoxyethyl)-2-imidazolydinone,1-methyl-3-(2-ethoxyethyl)-2-imidazolydinone and1,3-di-(2-ethoxyethyl)-2-imidazolydinone; and thiourea compounds whichinclude N-substituted cyclic thioureas such as those corresponding tothe above-recited N-substituted cyclic urea compounds;

imide compounds such as succinimide, N-methylsuccinimide, maleimide,N-methylmaleimide, phthalimide and N-methylphthalimide; carbamic acidcompounds isocyanuric acid compounds and derivatives thereof, such asmethyl carbamate, N,N-diethylcarbamate, isocyanuric acid andN,N′,N′-trimethylisocyanuric acid; and thiocarbonyl compounds such asthose corresponding to the above-recited compounds;

isocyanate compounds such as phenyl isocyanate and butyl ioscyanate; andthioisocyanate compounds such as phenylthioisocyanate;

silicon compounds having a halogen atom or an alkoxy group such astrimethylchlorosilane, triethylchlorosilane, triphenylchlorosilane,t-butyl-dimethylchlorosilane and trimethylethoxysilane; germaniumcompounds having a halogen atom or an alkoxy group such astrimethylgermanium chloride, triethylgermanium chloride,trimethylgermanium bromide and triphenylgermanium chloride; tincompounds having a halogen atom or an alkoxy group such as trimethyltinchloride, trimethyltin bromide, triethyltin chloride, triethyltinbromide, tripropyltin chloride, tri-n-butyltin chloride, triphenyltinchloride and triphenyltin fluoride; and phosphorus compounds having ahalogen atom or an alkoxy group such as dimethylchlorophosphine,diethylchlorophosphine, di-t-butylchlorophosphine,dicyclohexylchlorophosphine, diphenylchlorophosphine, diphenylphosphinicchloride, diphenylchlorophosphate and bis(dimethylamino)phosphorylchloride. Of these, the tin compounds are preferable. Halogenated tincompounds are more preferable.

To give terminal-modified polymers preferred as rubber materials, amongthe above-recited terminal modifiers, N-substituted amino ketones andcorresponding N-substituted amino thioketones, N-substituted lactams andcorresponding N-substituted thiolactams, N-substituted cyclic ureas andcorresponding N-substituted cyclic thioureas, imide compounds, carbamicacid compounds, isocyanuric acid compounds and derivatives thereof andcorresponding thiocarbonyl-containing compounds, isocyanate compoundsand thioisocyanate componds, and tin compounds having a halogen atom oran alkoxy group are prefeable. N-substituted amino ketones andcorresponding N-substituted amino thioketones, N-substituted lactams andcorresponding N-substituted thiolactams, and halogenated tin compoundsare more preferable.

To give a terminal-modified polymer suitable as a macromonomer, areagent having a reactive site capable of bonding to the living polymermolecule, and further having a polymerizable site is used as a terminalmodifier. Such a modifier includes, for example, vinylbenzyl chloride.

The amount of terminal modifier used is preferably in the range of 0.1to 1,000 mols, more preferably 0.2 to 100 mols and especially preferably0.5 to 10 mols, per mol of the transition metal compound (A).

The procedure by which a living polymer is contacted with a terminalmodifier is not particularly limited, but, the terminal modifier ispreferably incorporated in the polymerization system after theconversion of monomer exceeds 10%.

The temperature at which terminal modification is carried out is alsonot particularly limited. When a terminal modifier is incorporated in apolymerization system during progress of polymerization, the terminalmodification temperature is the same as the polymerization temperature,and is in the range of −100 to +100° C., preferably −80 to +60° C., morepreferably −70 to +40° C., and most preferably −60 to +20° C. Thereaction time for terminal modification is usually in the range of 1minute to 300 minutes.

The termination of terminal modification can be effected byincorporating a reaction stopper into the reaction system when apredetermined degree of terminal modification is reached. The reactionstopper includes, for example, alcohols such as methanol, ethanol,propanol, butanol and isobutanol. The stopper may contain an acid suchas hydrochloric acid. By the termination treatment, an unreacted livingpolymer becomes a dead polymer.

After termination of the terminal modification, the polymer isrecovered. The recovering process is not particularly limited. Forexample, a steam-stripping process and a precipitation method using apoor solvent are employed.

To stabilize the Mooney viscosity of a terminal-modified polymer asexhibited during storage, a Mooney viscosity stabilizer can be added inthe course spanning from the immediately after the completion ofterminal modification, to the drying step of polymer. The Mooneyviscosity stabilizer includes, for example, organic amino compounds suchas ethylamine, propylamine, butylamine, hexylamine, octadecylamine,aniline, naphthylamine, benzylamine, diphenylamine, triethylamine,dimethyloctadecylamine, m-phenylenediamine, p-phenylenediamine,N,N′-dimethyl-p-phenylenediamine, N,N′-dioctyl-p-phenylenediamine,N-propyl-N′-phenyl-p-phenylenediamine,N,N,N′,N′-tetrabutylethylenediamine, ethyleneimine, cyclohexeneimine,pyrrolidine, piperidine, morpholine, thiomorpholine, pyridine, pyrrole,pyrimidine, triazine, indole, quinoline and purine.

The amount of the Mooney viscosity stabilizer is not particularlylimited, but is preferably in the range of 0.1 to 40 mols, morepreferably 0.5 to 20 mols and most preferably 1 to 15 mols, as theamount of amino group per mol of a functional group derived from theterminal modifier bonded to polymer. If the amount of the Mooneyviscosity modifier is too small, the Mooney viscosity is liable to varyduring storage and the polymer sometimes become unsuitable for practicaluse. In contrast, if the amount thereof is too large, bleeding is liableto occur and the rate of curing at the step of curing becomes large toan uncontrollable extent.

An antioxidant is incorporated into the terminal-modified polymer in thecourse spanning from the immediately after the completion of terminalmodification, to the recovery of polymer. Especially when the polymer issubjected to a treatment accompanied by heat to be thereby heat-aged, anantioxidant is preferably added to the polymer before the heattreatment. The antioxidant may be added either alone or as a mixture ofat least two thereof. As specific examples of the antioxidant added tothe terminal-modified polymer, there can be mentioned those which arehereinbefore recited as for the antioxidant added to the conjugateddiene polymer. The amount of the antioxidant may also be the same as theamount of the antioxidant hereinbefore mentioned as for the conjugateddiene polymer.

Terminal-Modified Butadiene Polymer

The terminal-modified butadiene polymer of the present invention is ahomopolymer of butadiene or a copolymer of at least 50% by weight ofbutadiene with not more than 50% by weight of a monomer copolymerizabletherewith, and characterized in that the content of butadiene unitshaving a cis bond in the total butadiene units is at least 50%; thenumber average molecular weight (Mn) is in the range of 1,000 to10,000,000; the ratio (Mw/Mn) of weight average molecular weight (Mw) tonumber average molecular weight (Mn) is smaller than 3.0; a relationshiprepresented by the formula:

log(Mw/Mn)<0.162×log(Mw)−0.682

is satisfied between the weight average molecular weight (Mw) and theratio (Mw/Mn); and the butadiene polymer has at least 10%, based on thetotal polymer chains, of polymer chains having a functional group at aterminal thereof. That is, the terminal-modified polymer is acomposition comprising terminal-unmodified polymer molecules andterminal-modified polymer molecules, and the proportion (degree ofterminal modification) of the terminal-modified polymer molecules to thesum of the terminal-modified polymer molecules and theterminal-unmodified polymer molecules is at least 10%. The process forproducing the terminal-modified butadiene polymer may be the same asthat described above as for the process for producing theterminal-modified conjugated diene polymer.

The terminal-modified butadiene polymer of the present invention is ahomopolymer of butadiene or a copolymer comprising at least 50% byweight, preferably 70% by weight, more preferably at least 80% by weightand especially preferably at least 90% by weight of recurring unitsderived from 1,3-butadiene. A homopolymer of 1,3-butadiene is mostpreferable. If the proportion of the butadiene units is too small, theadvantage brought about by a large proportion of the cis-bond unitcontent in the butadiene polymer is lost.

The content of cis-bond units in the 1,3-butadiene units of theterminal-modified butadiene polymer is at least 50%, preferably at least80% and more preferably at least 90%. If the cis-bond unit content istoo small, tensile property and other property are deteriorated and thecharacteristics desired for rubber are lost. By the term “cis-bond unitcontent” used herein is meant the content of 1,4-cis-bond units.

The number average molecular weight (Mn) of the terminal-modifiedbutadiene polymer of the present invention as measured by GPC andexpressed as that of polybutadiene is in the range of 1,000 to10,000,000.

This polymer is classified into two types depending upon the usethereof: a high-molecular-weight terminal-modified butadiene polymerdesired for rubber material, and a low-molecular-weight butadienepolymer used as a macromonomer or a reactive prepolymer.

The first type of high-molecular weight butadiene polymer used as rubbermaterial has preferably an Mn in the range of 5,000 to 5,000,000, morepreferably 10,000 to 2,000,000, and most preferably 20,000 to 1,000,000.If Mn is too small, the mechanical strength and other properties as ahigh polymer are deteriorated. In contrast, Mn is too large, the polymeris difficult to shape.

The second type of high-molecular weight butadiene polymer used as amacromonomer or a reactive prepolymer has preferably an Mn in the rangeof 1,000 to 100,000 and more preferably 2,000 to 500,000. If Mn is toolarge, the reactivity as a macromonomer or a reactive prepolymer ispoor. In contrast, Mn is too small, the rubbery modification effect forthe polymer is poor.

The terminal-modified butadiene polymer of the present invention has amolecular weight distribution, i.e., a ratio (Mw/Mn) of the weightaverage molecular weight (Mw) to the number average molecular weight(Mn) is smaller than 3.0, preferably smaller than 2.5, more preferablysmaller than 2.0 and most preferably smaller than 1.5. If the molecularweight distribution is too large, abrasion resistance and otherproperties desired for a crosslinked product are deteriorated. If theabove formula (III) is not satisfied between Mw and Mw/Mn, theproperties desired for a cross-linked product are deteriorated.

When the terminal-modified butadiene polymer is produced by the processmentioned above as for the conjugated diene polymer, and therelationship between RMSR and MW are the same as those mentioned aboveas for the conjugated diene polymer.

The degree of terminal modification of the terminal-modified butadienepolymer is at least 10%, preferably at least 40%, more preferably atleast 60% and especially preferably at least 80%. By the above-mentionedprocess for producing the conjugated diene polymer, a living butadienepolymer having a living molecule chain content of larger than 80% can beobtained easily, and further by terminally modifying the livingbutadiene polymer, a terminal-modified butadiene polymer containing atleast 80% of molecule chains having a functional group bonded to themolecule chain based on the total molecule chains can be produced. Ifthe degree of terminal modification is too small, the mechanicalstrength and other properties desired for rubber material areinsufficient, and the reactivity of macromonomer or prepolymer is poor.

The degree of terminal modification is defined as percentage of thenumber of terminal-modified polymer molecules to the number of the totalpolymer molecules, and can be determined by measuring Mn of the polymerand the concentration of terminal-modified group. The Mn is measured byGPC or other means. The measurement of the concentration of theterminal-modified group varies depending upon the particular kind of theterminal modifier, but, methods of infrared absorption spectroscopy,¹H-NMR spectroscopy, ¹³C-NMR spectroscopy and GPC provided withultraviolet detector and differential refractometer.

Process for Producing Coupled Conjugated Diene Polymer

The coupled conjugated diene polymer of the present invention can beproduced by contacting the living conjugated diene polymer of thepresent invention or the living conjugated diene polymer produced by theprocess of the present invention with a reagent capable of reacting witha terminal having a transition metal bonded thereto of the livingpolymer, i.e., a coupling agent.

In the present invention, by the term “coupled polymer” we mean apolymer produced by allowing a plurality of living polymer molecules toreact with one molecule of a coupling agent to thereby form one polymermolecule.

The manner in which a coupled polymer is formed is classified into twotypes: first type coupling wherein a plurality of living polymermolecules are reacted with one molecule of coupling agent (e.g., tintetrachloride) having a plurality of functional groups capable ofreacting with the transition metal-bonded site of each polymer moleculeto form one coupled polymer molecule, and second type wherein one livingpolymer molecule is allowed to react with one molecule of coupling agent(e.g., N-methylpyrrolidone) to form a terminal-modified polymer, andthereafter two or more of the terminal-modified polymer are subjected toa chemical reaction or an after-treatment such as heat-treatment to forma coupled polymer. It is possible that the two types of coupling occursimultaneously in one reaction system.

As specific examples of the coupling agent, there can be mentionedrepresentative molecular oxygen, carbon monoxide, carbon dioxide, carbondisulfide, carbonyl sulfide and sulfur dioxide, and the followingcompounds.

Molecular halogens such as chlorine, bromine and iodine; and organichalides such as vinylbenzyl chloride and trimethylene bromide;

hetero-three-membered ring compounds which include epoxy compounds suchas ethylene oxide, propylene oxide, cyclohexene oxide, styrene oxide,epoxidized soybean oil, epoxidized natural rubber, bisphenol Adiglycidyl ether, glycerin triglycidyl ether andN,N,N′,N′-tetraglycidyl-diaminodiphenylmethane; thuirane compounds suchas thiurane, methylthurane and phenylthiirane; and ethyleneimine andderivatives thereof such as propyleneimine, N-penylethyleneimine,N-(β-cyanoethyl)ethyleneimine and 2,5-bis(1-aziridinyl)-p-benzoquinone,and propyleneimine;

ketones which include 2,5-hexanedione; N-substituted aminoketones suchas 4-dimethylaminoacetophenone, 4-diethylaminoacetophenone,1,3-bis(diphenylamino)-2-proanone,1,7-bis(methylethylamino)-4-heptanone, 4-dimethylaminobenozophenone,4-di-t-butylamino-benozophenone, 4-diphenylaminobenozophenone,4,4′-bis(dimethylamino)-benozophenone,4,4′-bis(diethylamino)-benozophenone and4,4′-bis(diphenylamino)benozophenone; and N-substituted aminothioketonessuch as those corresponding to the above-recited N-substitutedaminoketones;

aldehyde compounds which include pentanedial; N-substitutedbenzaldehydes such as 4-dimethylaminobenzaldehydes,4-diphenylaminobenzaldehydes and 4-divinylaminobenzaldehydes;N-substituted benzthioaldehydes such as those corresponding to theabove-recited N-substituted benzaldehydes; compounds having a ketenestructure such as ethylketene, butylketene, phenylketene andtoluylketene; compounds having a thioketene structure such asethylthioketene, butylthioketene, phenylthioketene and toluylthioketene;compounds having an ester structure such as ethyl acetate, fatty acidglycerol ester, glycerol triacetate and glycerol tributyrate; compoundshaving a lactone structure such as γ-butyrolactone; compounds having anacid halide structure such as propionyl chloride, benzoyl chloride,phthaloyl chloride, maleyl chloride and trimesoyl chloride; compoundshaving a carbodiimide structure such as N,N′-diphenylcarbodiimide andN,N′-diethylcarbodiimide;

pyridine compounds which include pyridine compounds having a halogen ona carbon atom adjacent to the nitrogen atom, such as2-amino-6-chloropyridine, 2,5-dibromopyridine,4-chloro-2-phenylquinazoline, 2,4,5-tribromoimidazole,3,6-dichloro-4-methylpyridazine, 3,4,5-trichloropyridazine,4-amino-6-chloro-2-mercaptopyrimidine,2-amino-4-chloro-6-methylpyrimidine, 2-amino-4,6-dichloropyrimidine,6-chloro-2,4-dimethoxypyrimidine, 2-chloropyrimidine,2,4-dichloro-6-methylpyrimidine, 4,6-dichloro-2-(methylthio)-pyrimidine,2,4,5,6-tetrachloropyrimidine, 2,4,6-trichloropyrimidine,2-amino-6-chloropyrazine, 2,6-dichloropyrazine,2,4-bis(methylthio)-6-chloro-1,3,5-triazine,2,4,6-trichloro-1,3,5-triazine, 2-bromo-5-nitrothiazole,2-chlorobenzothiazole and 2-chloro-benzoxazole; pyridyl-substitutedketones such as methyl-2-pyridylketone, methyl-4-pyridylketone,propyl-2-pyridylketone, di-4-pyridylketone, propyl-3-pyridylketone and2-benzoylpyridine; and vinylpyridines such as 2-vinylpyridine and4-vinylpyridine;

compounds having an amide structure, which includeN,N-dimethylformamide, acetamide, N,N-diethylacetamide, aminoacetamide,N,N-dimethyl-N′,N′-dimethylaminoacetamide, N,N-dimethylaminoacetamide,N,N-diethylaminoacetamide, N,N-dimethyl-N′-ethylaminoacetamide,acrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide,nicotinamide, isonicotinamide, picolinamide,N,N-dimethylisonicotinamide, succinamide, phthalamide,N,N,N′,N′-tetramethylphthalamide, oxamide, N,N,N′,N′-tetramethyloxamide,2-furancarboxylic acid amide, N,N-dimethyl-2-furancarboxylic acid amideand N-ethyl-N-methyl-quinolinecarboxylic acid amide; N-substitutedlactams such as N-methyl-β-propiolactam, N-phenyl-β-propiolactam,N-methyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone,N-phenyl-5-methyl-2-pyrrolidone, N-methyl-2-piperidone,N-phenyl-2-piperidone and N-methyl-ε-caprolactam; and N-substitutedthiolactams such as those corresponding to the above-recitedN-substituted lactams;

compounds having a urea structure which include urea and polymethyleneurea; N-substituted cyclic ureas such as 1,3-diethyl-2-imidazolidinone,1,3-dimethyl-2-imidazolidinone, 1,1-dipropyl-2-imidazolidinone,1-methyl-3-ethyl-2-imidazolidinone, 1-methyl-3-propyl-2-imidazolidinone,1-methyl-3-butyl-2-imidazolidinone,1-methyl-3-(2-methoxyethyl)-2-imidazolidinone,1-methyl-3-(2-ethoxyethyl)-2-imidazolidinone and1,3-di-(2-ethoxyethyl)-2-imidazolidinone; and compounds having athiourea structure which include N-substituted cyclic thioureas such asthose corresponding to the above-recited N-substituted cyclic ureas;

compounds having an imide structure such as succinimide,N-methylsuccinimide, maleimide, N-methylmaleimide, phthalimide,N-methylphthalimide and polyimide; compounds having a carbamic acidstructure, compounds having an isocyanuric acid structure and compoundshaving a structure derived therefrom, such as methyl carbamate,N,N-diethylcarbamate, isocyanuric acid and N,N′,N′-trimethylisocyanuricacid; and thiocarbonyl compounds such as those corresponding to theabove-recited compounds;

compounds having an isocyanate structure such as 2,4-tolylenediisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate,1,3,5-benzene triisocyanate and polymeric type diphenylmethanediioscyanate, isophorone diisocyanate and hexamethylene diisocyanate;and compounds having a thioisocyanate structure such as 2,4-tolylenedithioisocyanate and hexamethylene dithioisocyanate;

silicon compounds having a halogen atom or an alkoxy group such ashexachlorodisilane, bis(trichlorosilyl)ethane, silicon tetrachloride,silicon tetrabromide, silicon tetrafluoride, silicon tetraiodide,tetramethoxysilane, tetraethoxysilane, trichloromethylsilane,ethyltrichloro-silane, n-butyltrichlorosilane, phenyltrichlorosilane,vinyltrichlorosilane, methyltrimethoxysilane, phenyltrimethoxysilane,3-aminopropyltriethoxysilane, dimethyldichlorosilane,diphenyldichlorosilane, methyldichlorosilane,methylphenyldichlorosilane, dimethyldiethoxysilane anddiphenyldimethoxysilane;

germanium compounds having a halogen atom or an alkoxy group such asgermanium tetrachloride, germanium tetrabromide, germanium tetraiodide,germanium tetraethoxide, ethylgermanium trichloride, germanium diuodide,dimethylgermanium dichloride and diethylgermanium dichloride;

tin compounds having a halogen atom or an alkoxy group such asbis(trichlorostanyl)ethane, tin tetrachloride, tin tetrabromide, tintetraiodide, tin tetrafluoride, tetra-t-butoxytin, methyltintrichloride, phenyltin trichloride, n-butyltin trichloride, tindichloride, tin dibromide, tin diodide, tin difluoride, dimethyltindichloride, di-n-butyltin dichloride, di-t-butyltin dichloride,diphenyltin dichloride, divinyltin dichloride and diethoxytin;

phosphorus compounds having a halogen atom or an alkoxy group such asphosphorus pentachloride, phosphorus pentabromide, phosphoruspentafluoride, bis-(dichlorophosphino)methane,1,2-bis(dichlorophosphino)-ethane,1,2-bis(dichlorophosphino)-1,2-dimethylhydrazine, phosphorustrichloride, phosphorus tribromide, phosphorus triiodide, phosphorustrifluoride, thiophosphoryl chloride, methyldichlorophosphine,ethyldichlorophosphine, t-butyldichlorophosphine,phenyldichlorophosphine, phenyldichlorophosphine oxide anddibromotriphenyl-phosphorane.

To provide coupled polymers preferred as rubber material, among theabove-recited coupling agents, compounds having a ketone structure,compounds having an ester or lactone structure, compounds having anamido structure, compounds having an isocyanate or thioisocyanatestructure, silicon compounds having a halogen atom or an alkoxy group,germanium compounds having a halogen atom or an alkoxy group, tincompounds having a halogen atom or an alkoxy group and phosphoruscompounds having a halogen atom or an alkoxy group are preferable.N-substituted lactams, corresponding N-substituted lactams, and tincompounds having a halogen atom or an alkoxy group are especiallypreferable. Tin tetrachloride is most preferable.

The amount of coupling agent used is preferably in the range of 0.01 to1,000 mols, more preferably 0.05 to 100 mols and especially preferably0.1 to 10 mols, per mol of the transition metal compound (A).

The procedure by which a living polymer is contacted with a couplingagent is not particularly limited, but, the coupling agent is usuallyincorporated in the polymerization system. The incorporation of couplingagent is generally conducted after the conversion of monomer exceeds10%.

The temperature at which coupling is carried out is also notparticularly limited. When a polyfunctional reagent is used as thecoupling agent, and it is incorporated in a polymerization system duringprogress of polymerization, the coupling temperature is the same as thepolymerization temperature, and is in the range of −100 to +100° C.,preferably −80 to +60° C., more preferably −70 to +40° C., and mostpreferably −60 to +20° C. The reaction time for coupling is usually inthe range of 1 minute to 300 minutes.

The termination of coupling reaction can be effected by incorporating areaction stopper into the reaction system when a predetermined degree ofcoupling is reached. The reaction stopper includes, for example,alcohols such as methanol, ethanol, propanol, butanol and isobutanol.The stopper may contain an acid such as hydrochloric acid. By thetermination treatment, an unreacted living polymer becomes a deadpolymer.

After termination of the coupling reaction, the polymer is recovered.The recovering process is not particularly limited. For example, asteam-stripping process and a precipitation method using a poor solventare employed. Thereafter, according to the need, a residual solvent isremoved, for example, by heat-drying to recover a coupled polymer.

To stabilize the Mooney viscosity of a coupled polymer as exhibitedduring storage, a Mooney viscosity stabilizer can be added in the coursespanning from the immediately after the completion of coupling reaction,to the drying step of polymer. The Mooney viscosity stabilizer includesthose which are recited as for the stabilization of a terminal-modifiedpolymer.

The amount of the Mooney viscosity stabilizer is not particularlylimited, but is preferably in the range of 0.1 to 40 mols, morepreferably 0.5 to 20 mols and most preferably 1 to 15 mols, as theamount of amino group per mol of a functional group of the couplingagent. If the amount of the Mooney viscosity modifier is too small, theMooney viscosity is liable to vary during storage and the polymersometimes become unsuitable for practical use. In contrast, if theamount thereof is too large, bleeding is liable to occur and the rate ofcuring at the step of curing becomes large to an uncontrollable extent.

An antioxidant is incorporated into the coupled polymer in the coursespanning from the immediately after the completion of coupling reaction,to the recovery of polymer. Especially when the polymer is subjected toa treatment accompanied by heat to be thereby heat-aged, an antioxidantis preferably added to the polymer before the heat treatment. Theantioxidant may be added either alone or as a mixture of at least twothereof. As specific examples of the antioxidant added to the coupledpolymer, there can be mentioned those which are hereinbefore recited asfor the antioxidant added to the conjugated diene polymer. The amount ofthe antioxidant may also be the same as the amount of the antioxidanthereinbefore mentioned as for the conjugated diene polymer.

Coupled Polymer

The coupled polymer is obtained as a composition comprising uncoupledpolymer molecules and coupled polymer molecules. Sometimes, thecomposition comprises coupled polymers comprised of different number ofbound conjugated diene polymer molecules. The coupled polymer ofdifferent number of bound conjugated diene polymer molecules may beclassified into two or more polymers having different molecular weights,but usually the composition is used as it is as a coupled polymer.

The coupled butadiene polymer of the present invention is a compositioncomprising (I) 0 to 90 parts by weight of a polymer which is ahomopolymer of butadiene or a copolymer of butadiene with a monomercopolymerizable therewith, in which the content of butadiene unitshaving a cis-bond in the total butadiene units is at least 50%, thenumber average molecular weight (Mn) is in the range of 1,000 to10,000,000; and (II) 100 to 10 parts by weight of a polymer composed ofat least two molecules of the above-mentioned polymer (I), bondedthrough a coupling agent. The coupled butadiene polymer can be producedby the above-mentioned process for the production of a conjugated dienepolymer.

The coupled butadiene polymer of the present invention is a homopolymerof butadiene or a copolymer comprising at least 50%, preferably at least70%, more preferably at least 80% and especially preferably at least 90%of recurring units derived from 1,3-butadiene. A homopolymer of1,3-butadiene is most preferable. If the proportion of the butadieneunits is too small, the advantage brought about by a large proportion ofthe cis-bond unit content in the butadiene polymer is lost.

The content of cis-bond units in the 1,3-butadiene units of the coupledbutadiene polymer is at least 50%, preferably at least 80% and morepreferably at least 90%. If the cis-bond unit content is too small,tensile property and other property are deteriorated and thecharacteristics desired for rubber are lost. By the term “cis-bond unitcontent” used herein is meant the content of 1,4-cis-bond units.

The number average molecular weight (Mn) of polymer (I) in the coupledbutadiene polymer composition of the present invention as measured byGPC and expressed as that of polybutadiene is in the range of 1,000 to10,000,000, preferably 5,000 to 5,000,000, more preferably 10,000 to1,000,000 and most preferably 20,000 to 500,000. If Mn is too small, themechanical strength and other properties as a high polymer aredeteriorated. In contrast, Mn is too large, the polymer is difficult toshape.

Polymer (I) in the coupled butadiene polymer composition of the presentinvention has a molecular weight distribution, i.e., a ratio (Mw/Mn) ofthe weight average molecular weight (Mw) to the number average molecularweight (Mn), of preferably smaller than 3.0, more preferably smallerthan 2.0, and most preferably smaller than 1.5. If the molecular weightdistribution is too large, abrasion resistance and other propertiesdesired for a crosslinked product are deteriorated.

Polymer (I) in the coupled butadiene polymer composition of the presentinvention preferably satisfies a relationship of weight averagemolecular weight (Mw) with the ratio (Mw/Mn) of weight average molecularweight (Mw) to number average molecular weight (Mn), represented by thefollowing inequality (γ), provided that A=0.162 and B=0.682.

log(Mw/Mn)<A×log(MW)−B  (γ)

The relationship of inequality (γ) is satisfied preferably provided thatA=0.161, more preferably A=0.160 and especially preferably A=0.159, andpreferably provided that B=0.684, more preferably B=0.687, andespecially preferably B=0.690.

Polymer (I) in the coupled butadiene polymer composition of the presentinvention is preferably substantially free from a branched structure.The branched structure of polymer (I) is evaluated by the relationshipof the root mean square radius (“RMSR”, in nm) determined by measurementof GPC-multi-angle light scattering (MALLS), with the absolute molecularweight (MW, in g/mol). In this measurement, tetrahydrofuran is used aselute and the measurement is conducted at a temperature of 40±2° C. Bythe term “branched structure” used herein, we mean polymer structuresformed by elementary reactions including shift reaction, other thannormal addition reaction, of monomer. It is not meant a branched-chainvinyl structure derived from 1,2-bond, nor a long chain branchedstructure formed by a coupling reaction. The branched structure ofpolymer (I) in the coupled butadiene polymer composition of the presentinvention preferably satisfies a relationship of RMSR (nm) with MW(g/mol), represented by the following inequality (δ).

log(RMSR)>a×log(MW)−b  (δ)

In inequality (δ), “a” is 0.638, and “b” is 2.01, preferably not largerthan 2.00 and more preferably not larger than 1.99. The butadienepolymer satisfying inequality (δ) is formed by a living polymerization,and is substantially free from a branched structure and has a highcontent of cis-bond units.

The coupled butadiene polymer composition of the present inventioncomprises a polymer (II) composed of at least two molecules of theabove-mentioned polymer (I), bonded through a coupling agent. Thecontent of polymer (II) in the coupled butadiene polymer composition,i.e., degree of coupling, is at least 10%, preferably at least 20% andmore preferably at least 30%. The upper limit of the content of polymer(II) is not particularly limited and may be up to 100%. If the contentof polymer (II) is too small, improved benefits brought about bycoupling including improvement of dimensional stability at roomtemperature are poor.

The degree of coupling (% by weight) can be calculated from a peak areaof a molecule of butadiene polymer (I) and a peak area of a molecule ofcoupled butadiene polymer (II) in the GPC curve. Note, a molecule ofbutadiene polymer to which a molecule of coupling agent has not beenbound, and a molecule of butadiene polymer to which a molecule ofcoupling agent has been bound cannot be substantially distinguished fromeach other by GPC. Therefore, these two types butadiene polymers areregarded as butadiene polymer (I) in the present invention.

The molecular weight of coupled polymer (II) in the coupled butadienepolymer composition of the present invention is at least twice,preferably at least three times, of that of polymer (I).

The molecular shape of coupled butadiene polymer (II) in the coupledbutadiene polymer composition of the present invention is straightchain-like when the coupled polymer (II) is composed of two molecules ofpolymer (I), or is star-shaped when the coupled polymer (II) is composedof at least three molecules of polymer (I). The star-shaped coupledbutadiene polymer is more preferred than the straight chain-shapedcoupled butadiene polymer.

The chemical structure of the coupled site of coupled butadiene polymermolecule (II) in the coupled butadiene polymer composition of thepresent invention is not particularly limited, but preferably has atin-butadienyl bond.

The present invention will now be specifically described by thefollowing working examples.

REFERENCE EXAMPLE 1 Synthesis of(2-Methoxycarbonylmethyl)-cyclopentadienyl-trichlorotitanium[MeO(CO)CH₂CpTiCl₃]

A solution of 30.6 g (200 mmol) of methyl bromoacetate in 100 ml oftetrahydrofuran (hereinafter abbreviated to “THF”) was graduallydropwise added to a solution of 32 g (200 mmol) oftrimethylsilylcyclopentadienylsodium in 400 ml of THF while beingstirred in an argon atmosphere at −78° C. After completion of theaddition, the reaction mixture was further maintained at −78° C.overnight with stirring. Then THF was distilled off under a reducedpressure from the reaction mixture, and the obtained solid was filteredoff and subjected to vacuum distillation (65-66° C./3 mmHg) to giveabout 30 g of (2-methoxycarbonylmethyl)trimethylsilylcyclopentadiene[TMSCpCH₂COOMe]. Yield: 70%. The chemical structure was confirmed by thefollowing data obtained by ¹H-NMR using CDCl₃.

¹H-NMR (ppm, TMS, CDCl₃): 6.55-6.20 (m, ring H bound to C of double bondin Cp), 3.5-3.35 (m, ring H bound to C of single bond in Cp), 3.15-2.98(m, ring H bound to C of single bond in Cp), 3.69 (s, 2H), 3.67 (s, 3H),−0.22 (s, 9H).

To a solution of 4.2 g (20 mmol) of(2-methoxycarbonylmethyl)trimethylsilylcyclopentadiene in 100 ml of drymethylene chloride, 3.8 g (20 mmol) of titanium tetrachloride was addedwhile being stirred at 0° C. in an argon atmosphere. The mixture wasstirred at room temperature for 3 hours. The reaction mixture was cooledto −30° C. to precipitate 4.0 g of orange crystal. Yield: 70%. Thechemical structure was confirmed by the following data obtained by¹H-NMR using CDCl₃.

¹H-NMR (ppm, TMS, CDCl₃): 7.05 (s, 4H), 3.92 (s, 2H), 3.76 (s, 3H).

REFERENCE EXAMPLE 2 Synthesis of(2-Methoxyethyl)cyclopentadienyl-trichlorotitanium (MeOCH₂CH₂CpTiCl₃)

A solution of 18.9 g (200 mmol) of chloroethyl methyl ether in 100 ml ofTHF was gradually dropwise added to a solution of 32 g (200 mmol) oftrimethylsilyl-cyclopentadienylsodium in 400 ml of THF while beingstirred in an argon atmosphere at −78° C. After completion of theaddition, the reaction mixture was heated under reflux overnight. ThenTHF was distilled off under a reduced pressure, and the obtained solidwas filtered off and subjected to vacuum distillation (80° C./1 mmHg) togive about 33 g of [(2-methoxy)ethyl]-trimethylsilylcyclopentadiene(TMSCpCH₂CH₂OMe). Yield: 85%. The chemical structure was confirmed bythe following data obtained by ¹H-NMR using CDCl₃.

¹H-NMR (ppm, TMS, CDCl₃): 6.55-6.20 (m, ring H bound to C of double bondin Cp), 3.5-3.35 (m, ring H bound to C of single bond in Cp), 3.15-2.98(m, ring H bound to C of single bond in Cp), 3.61 (m, 2H), 3.40 (s, 3H),3.02 (m, 2H), 0.22 (s, 9H).

To a solution of 0.50 g (2.5 mmol) of the thus-obtained TMSCpCH₂CH₂OMein 20 ml of dry methylene chloride, 0.25 ml (2.2 mmol) of titaniumtetrachloride was added while being stirred at −78° C. in an argonatmosphere. The mixture was stirred at room temperature for 3 hours. Thereaction mixture was cooled to −78° C. to precipitate 0.43 g of orangecrystal. Yield: 70%. ¹H-NMR analysis using CDCl₃ revealed that theproduct was (2-methoxyethyl)cyclopentadienyl-trichlorotitanium(MeOCH₂CH₂CpTiCl₃).

¹H-NMR (ppm, TMS, CDCl₃): 6.91 (s, 4H), 3.70 (t, 2H), 3.37 (s, 3H), 3.10(t, 2H)

REFERENCE EXAMPLE 3 Synthesis ofTrimethylsilylcyclopentadienyl-trichlorotitanium (Me₃SiCpTiCl₃)

Bis(trimethylsilyl)cyclopentadiene was synthesized by a method describedin J.C.S. Dalton, 1980, p1156, followed by purification by distillationunder reduced pressure.

To a solution of 2.1 g (10 mmol) of the thus-producedbis(trimethylsilyl)cyclopentadiene in 100 ml of dry hexane, 1.1 ml (10mmol) of titanium tetrachloride was dropwise added while being stirredin an argon atmosphere at −78° C. After completion of the addition, thereaction mixture was further stirred for 4 hours. Then solvent wasdistilled off under a reduced pressure, and the obtained solid wassubjected to sublimation to give 2.1 g of yellow crystal. Yield: 85%.The chemical structure of Me₃SiCpTiCl₃ was confirmed by the followingdata obtained by ¹H-NMR using CDCl₃.

¹H-NMR (ppm, TMS, CDCl₃): 6.85 (t, 2H), 6.66 (t, 2H), 0.10 (s, 9H).

EXAMPLE 1

A pressure-resistant glass flask having an inner volume of 300 ml andequipped with a stirrer was charged with 86.6 g of toluene and asolution of 75.0 mmol of methylaluminoxane in toluene (supplied byTosoh-Akzo Co.), and the content was maintained at a constanttemperature of 25° C. A solution of 0.075 mmol of(2-methoxycarbonylmethyl)cyclopentadienyl-trichlorotitanium[MeO(CO)CH₂CpTiCl₃, hereinafter abbreviated to “TiES”] was added, andthe mixture was aged at 25° C. for 5 minutes. Then the content wasrapidly cooled to a constant temperature of −25° C. Then 2.35 g ofbutadiene was charged therein to commence first polymerization whilebeing stirred at −25° C. When 8 minutes elapsed from the commencement offirst polymerization, 10 g of the polymerization liquid was sampled todetermine the degree of polymerization and conduct GPC analysis. When 10minutes elapsed from the commencement of first polymerization, 6.13 g ofbutadiene was added to carried out second polymerization at −25° C. for100 minutes. An aqueous acidic methanol was added to terminate thepolymerization, and the polymerization liquid was poured into a salientamount of an aqueous acidic methanol to precipitate a polymer. Thepolymer was dissolved in toluene, and the polymer solution was subjectedto centrifugal separation to remove the ash content, and then a polymerwas reprecipitated from an aqueous acidic methanol. The thus-obtainedpolymer was dried and weighed to determine yield of the polymer.

The microstructure of polymer was determined by NMR analysis as follows.The ratio of 1,4-bond to 1,2-bond in the polymer was determined by¹H-NMR analysis (1,4-bond 5.4-5.6 ppm, 1,2-bond 5.0-5.1 ppm). The ratioof cis-bond to trans-bond was calculated from C-NMR (cis 28 ppm, trans33 ppm), thus determining the cis-bond content in the total polymer.

The number average molecular weight (Mn) and the molecular weightdistribution as expressed by the ratio (Mw/Mn) were determined by gelpermeation chromatography (GPC) analysis. For the GPC analysis, twoconnected columns (GMH supplied by Tosoh Corp.), or column G-7000connected to column G-5000 was used. The molecular weight was determinedfrom a calibration curve drawn by using a standard polybutadienespecimen (supplied by Polymer Laboratories Co.).

The results of the NMR analysis and the GPC analysis were as follows.

(1) First polymerization; Polymer yield: 100%, Mn: 73,000, Mw/Mn: 1.43

(2) Second polymerization; Polymer yield: 100%, Mn: 463,000, Mw/Mn:1.09, cis-bond content: 93%, trans-bond content: 2%, 1,2-bond content:5%.

From GPC eluation curves of polymer, it was confirmed that the peak ofpolymer obtained in the first polymerization completely disappeared inthe GPC curve of polymer obtained in the second polymerization.

It will be seen from the results in Example 1 that butadiene is subjectto living polymerization at an extremely high rate (i.e., polymerizationactivity was very high), the content of living polymer chain is 100%,the cis-bond content is high, the molecular weight is large and themolecular weight distribution is very narrow.

EXAMPLE 2

A solution of 0.0244 mmol of TiES in toluene was dropwise added to asolution of 24.4 mmol of methylaluminoxane in toluene, and the mixturewas maintained at 25° C. for 5 minutes to effect aging.

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 52.4 g of toluene and 5.5 g of butadiene in anitrogen atmosphere, and the content was cooled to −25° C. Theabove-mentioned aged catalyst was added into the ampoule to carry outpolymerization at −25° C. for 3 minutes. Thereafter a small amount of anaqueous acidic methanol was added to terminate the polymerization, andthe polymerization liquid was poured into a salient amount of an aqueousacidic methanol to precipitate a white solid. The solid was filtered andthen dried to give a butadiene polymer.

The yield of polymer was 100%. The polymerization results are shown inTable 1.

The polymerization activity as expressed by the yield of polymer per 1mmol of transition metal in the transition metal compound used forpolymerization and per hour of reaction time was 4,700 g/mmol-M·h.

The branched structure of polymer was determined by GPC-multi-anglelight scattering (MALLS) measurement. The GPC-MALLS measurement wasconducted at 40±2° C. by using a multi-angle light scattering detector(“DAWN-F” supplied by Wyatt Technology Corporation), two connectedcolumns G-7000 and G-5000 (both supplied by Tosoh Corp.) as column, andTHF as eluting liquid. The relationship of the root mean square radius(RMSR, nm) with the absolute molecular weight (MW, g/mol), representedby the inequality (II), was determined in a molecular weight regionwherein the measured values were significant. In inequality (II),factors “c” and “d” were 0.655 and 2.08, respectively. By the termRMSR(100) and RMSR(50) occurring in Table 1 we mean values of RMSRcorresponding to molecular weights of 1,000,000 and 500,000,respectively.

COMPARATIVE EXAMPLES 1 AND 2

For comparison, a butadiene polymer (“Neocis 60” supplied by Enichem)prepared by using a commercially available neodymium catalyst, and abutadiene polymer (“Nipol BR1220” supplied by Zeon Corp.) prepared by acommercially available cobalt catalyst were analyzed by the same methodsas described in Example 2. The results are shown in Table 1.

TABLE 1 Comparative Comparative Example 2 Example 1 Example 2 CatalystTiES Nd Co Aging +25° C., 5 min — — Polymn. temp. −25 — — (° C.) BD/Ti*1250 — — (g/mmol) Polymn. time (h) 0.05 — — Yield (%) 100 — — Polymn.activity 4,700 — — Cis content (%) 92 97 98 10⁻⁴ Mn 37.8 15.5 13.5 Mw/Mn1.21 3.52 2.31 a 0.655 0.638 0.523 b 2.08 2.01 1.40 RMSR(100) 70.8 65.854.7 RMSR(50) 45.0 42.3 38.1 *BD/Ti: Amount of butadiene (g) per mmol oftitanium in catalyst

As seen from Table 1, polymerization by the process of the presentinvention proceeds with high activity, and the obtained polymer has highcis-content, high molecular weight, narrow molecular weight distributionand reduced amount of branched structure.

EXAMPLES 3-10, AND COMPARATIVE EXAMPLE 3

By using TiES as a transition metal compound and employing theconditions shown in Table 2, polymerization and analysis of polymer werecarried out by the same methods as described in Example 2. The resultsare shown in Table 2.

TABLE 2 Example No. 3 4 2 5 6 C3* 7 8 9 10 Catalyst TiES TiES TiES TiESTiES TiES TiES TiES TiES TiES Aging [Temp. (° C.) × +25 × +25 × +25 ×+25 × +25 × +25 × −25 × −25 × −25 × −25 × Time (min.)] 5 5 5 5 5 5 60 6060 60 Polymn. Temp. (° C.) −25 −25 −25 −25 0 +25 0 0 −25 −25 BD/Ti*(g/mmol) 500 500 250 100 250 500 500 500 500 500 Polymn. time (h) 0.050.117 0.05 0.05 0.183 0.217 0.08 0.167 0.33 0.5 Yield (%) 37 83 100 10063 85 28 60 38 57 Polymn. activity 3,500 3,300 4,700 1,900 860 980 1,6001,600 520 510 Cis content (%) 92 92 92 92 92 92 93 93 93 93 10⁻⁴ Mn 4269 38 19 61 18 91 106 105 146 Mw/Mn 1.13 1.36 1.21 1.17 1.15 2.58 1.411.67 1.37 1.51 *C3: Comparative Example 3 BD/Ti*: Amount of butadienemonomer (g) per mmol of titanium in catalyst

As seen from Table 2, at a polymerization temperature of −25° C. and 0°C., the number average molecular weight increases with an increase ofthe yield of polymer and a narrow molecular weight distribution ismaintained. The number average molecular weight is controlled by theratio of monomer/catalyst. Further, in Examples 3, 5 and 6, high-cis andsubstantially monodisperse butadiene polymers are obtained. From thesefactual data, it was confirmed that polymers obtained in Example 2 andExamples 3 to 10 contain at least 80% of living polymer chains.

EXAMPLES 11-16, AND COMPARATIVE EXAMPLES 4-6

By using (2-methoxyethyl)cyclopentadienyl-trichlorotitaniumMeOCH₂CH₂CpTiCl₃ (hereinafter abbreviated to “TiET”) as a transitionmetal compound and employing the conditions shown in Table 3,polymerization and analysis of polymer were carried out by the samemethods as described in Example 2. The results are shown in Table 3.

As seen from Table 3, the number average molecular weight increases withan increase of the yield at a polymerization temperature of −25° C. and0° C., but does not increase at a polymerization temperature of 25° C.Thus, it was confirmed that a living polymerization proceeded place inExamples 11 to 16.

TABLE 3 Example No. 11 12 13 14 15 16 C4* C5* C6* Catalyst TiET TiETTiET TiET TiET TiET TiET TiET TiET Aging [Temp. (° C.) × −25 × −25 × −25× −25 × −25 × −25 × −25 × −25 × −25 × Time (h)] 2 2 2 2 2 2 2 2 2Polymn. temp. (° C.) 0 0 0 −25 −25 −25 +25 +25 +25 BD/Ti* (g/mmol) 250250 250 500 500 500 250 250 250 Polymn. time (h) 2 20 100 2 20 100 2 420 Yield (%) 16 32 43 5 12 32 42 58 81 Polymn. activity 18 3.6 0.97 112.7 1.4 47 33 9.1 Cis content (%) 96 96 96 98 98 98 96 96 96 10⁻⁴ Mn 5986 108 51 123 194 30 34 33 Mw/Mn 2.03 2.38 2.19 1.63 1.86 1.62 1.98 1.862.03 *C4, C5 and C6: Comparative Examples 4, 5 and 6 BD/Ti*: Amount ofbutadiene monomer (g) per mmol of titanium in catalyst

EXAMPLES 17 AND 18, AND COMPARATIVE EXAMPLE 7

By using trimethylsilylcyclopentadienyl-trichlorotitanium (hereinafterabbreviated to “TiTMS”) as a transition metal compound and employing theconditions shown in Table 4, polymerization and analysis of polymer werecarried out by the same methods as described in Example 2. The resultsare shown in Table 4.

TABLE 4 Example No. 17 18 C7* Catalyst TiTMS TiTMS TiTMS Aging [Temp. (°C.) × +25 × 5 +25 × 5 +25 × 5 Time (min.)] Polymn. Temp. (° C.) −25 −2525 BD/Ti* (g/mmol) 250 100 250 Polymn. time (h) 1 1 0.25 Yield (%) 61 94100 Polymn. activity 150 94 1,000 Cis Content (%) 89 89 89 1 CT⁴ Mn 4424 35 Mw/Mn 1.10 1.12 2.15 *C7: Comparative Example 7 BD/Ti: Amount ofbutadiene (g) per mmol of titanium in catalyst

As seen from Table 4, a substantially monodisperse polymer having anarrow molecular weight distribution is obtained at a polymerizationtemperature of −25° C., whereas a polymer having a relatively broadmolecular weight distribution is obtained at a polymerizationtemperature of 25° C. Thus, it was confirmed that a livingpolymerization proceeded in Examples 17 and 18.

EXAMPLES 19 AND 20

By using TiTMS as a transition metal compound,triphenylcarboniumtetra(pentafluorophenyl)borate as catalyst ingredient(B), and triisobutylaluminum (hereinafter abbreviated to “TIBA”) asthird catalyst ingredient, polymerization and analysis of polymer werecarried out by the same methods as described in Example 17. Thepolymerization conditions employed and the results obtained are shown inTable 5.

TABLE 5 Example No. 19 20 Catalyst TiTMS TiTMS Aging [Temp. (° C.) × −40× 30 −40 × 30 Time (min.)] Polymn. Temp. (° C.) −40 −40 BD/Ti*(mmol/mmol) 100 100 B/Ti* (mmol/mmol) 1 1 Al/Ti* (g/mmol) 10 10 Polymn.time (h) 2 6 Yield (%) 10 20 Polymn. activity 5 3.3 Cis content (%) 9393 10⁻⁴ Mn 4.8 9.7 Mw/Mn 1.07 1.11 *BD/Ti: Amount of butadiene (g) permmol of titanium in catalyst B/Ti: Amount of catalyst ingredient (B)(mmol) per mmol of titanium in catalyst Al/Ti: Amount of aluminum (mmol)in TIBA per mmol of titanium in catalyst

As seen from Table 5, Mn increases with an increase of the yield and thepolymer obtained is substantially monodisperse. Thus, it was confirmedthat a living polymerization proceeded in Examples 18 and 19.

EXAMPLES 21 AND 22

By using cyclopentadienyltrichlorotitanium (hereinafter abbreviated to“CpTiCl₃”) as a transition metal compound, polymerization and analysisof polymer were carried out by the same methods as described in Example2. As CpTiCl₃, that was purified by recrystallization from methylenechloride at −35° C. was used. The polymerization conditions and resultsare shown in Table 6.

TABLE 6 Example No. 21 22 Catalyst CpTiCl₃ CpTiCl₃ Aging [Temp. (° C.) ×+25 × 5 +25 × 5 Time (min.)] Polymn. Temp. (° C.) −25 −25 BD/Ti*(g/mmol) 250 100 Polymn. time (h) 24 24 Yield (%) 64 85 Polymn. activity7 4 Cis content (%) 84 84 10⁻⁴ Mn 48 29 Mw/Mn 1.09 1.07 *BD/Ti: Amountof butadiene (g) per mmol of titanium in catalyst

As seen from Table 6, a substantially monodisperse polymer having anarrow molecular weight distribution is obtained at −25° C. Thus, it wasconfirmed that a living polymerization proceeded in Examples 21 and 22.

EXAMPLES 23 AND 25, AND COMPARATIVE EXAMPLE 8

By using CpTiCl₃ as a transition metal compound, triphenylcarboniumtetra(pentafluorophenyl)borate as catalyst ingredient (B), and TIBA as thirdcatalyst ingredient, polymerization and analysis of polymer were carriedout by the same methods as described in Example 21. The polymerizationconditions employed and the results obtained are shown in Table 7.

As seen from Table 7, Mn increases with an increase of the yield and asubstantially monodisperse polymer having a narrow molecular weightdistribution is obtained at a polymerization temperature of −25° C. Incontrast, a polymer having many peaks in the molecular weightdistribution curves is obtained at a polymerization temperature of 25°C. Thus, it was confirmed that a living polymerization proceeded inExamples 23 to 25.

TABLE 7 Example No. 23 24 25 C8 Catalyst CpTiCl₃ CpTiCl₃ CpTiCl₃ CpTiCl₃Aging [Temp. (° C.) × −25 × 20 −25 × 20 −25 × 20 +25 × 20 Time (min.)]Polymn. Temp. (° C.) −25 −25 −25 +25 BD/Ti* (g/mmol) 100 100 100 40B/Ti* (mmol/mmol) 1 1 1 1 Al/Ti* (mmol/mmol) 10 10 10 10 Polymn. time(h) 1 3 5 1 Yield (%) 22 35 43 100 Polymn. activity 22 12 9 40 Ciscontent (%) 89 89 89 10⁻⁴ Mn 5.0 8.7 11.7 — Mw/Mn 1.11 1.09 1.11 multi-modal *C8: Comparative Example 8 BD/Ti: Amount of butadiene (g) per mmolof titanium in catalyst B/Ti: Amount of catalyst ingredient (B) (mmol)per mmol of titanium in catalyst Al/Ti: Amount of aluminum (mmol) inTIBA per mmol of titanium in catalyst

EXAMPLE 26

A solution of 0.0122 mmol of TiET in toluene was dropwise added to asolution of 12.2 mmol of methylaluminoxane in toluene (supplied byTosoh-Akzo Co.), and the mixture was maintained at −25° C. for one hourto effect aging.

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 52.4 g of toluene and 5.5 g of butadiene in anitrogen atmosphere, and the content was maintained at 25° C. Theabove-mentioned aged catalyst was added into the ampoule to carry outpolymerization at +25° C. for 4 hours. Thereafter a small amount of anaqueous acidic methanol was added to terminate the polymerization, andthe polymerization liquid was poured into a salient amount of an aqueousacidic methanol to precipitate a white solid. The solid was filtered andthen dried to give a butadiene polymer. The yield of polymer was 36%.

The polymerization activity was 41 g/mmol-M·h, the cis-bond content was97%, Mn was 350,000 and Mw/Mn was 1.92.

The initiator efficiency (E.I.) was 53% as expressed by the followingformula X, i.e., the ratio of theoretical molecular weight (Mk) to Mn asdetermined by GPC measurement.

E.I.=Mk/Mn  (X)

wherein Mk is calculated from the following formula (Y):

Mk=(yield of polymer, weight %)×(amount of butadiene used forpolymerization, g)/(amount of Ti in catalyst, mol)  (Y)

The polymerization conditions and results are shown in Table 8.

EXAMPLE 27

Polymerization of butadiene and analysis of polymer were carried out bythe same methods as described in Example 26 except that thepolymerization time was changed to 20 hours. The results are shown inTable 8.

COMPARATIVE EXAMPLE 9

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 52.4 g of toluene and 5.5 g of butadiene in anitrogen atmosphere, and the content was maintained at +25° C. Into thisglass ampoule, a solution of 12.2 mmol of methylaluminoxane in toluene(supplied by Tosoh-Akzo Co.) and a solution of 0.0122 mmol of TiET intoluene were added in this order to carried out polymerization at +25°C. for 4 hours. After-treatments and analysis of polymer were carriedout by the same procedures as described in Example 26.

The results are shown in Table 8.

COMPARATIVE EXAMPLE 10

Polymerization of butadiene and analysis of polymer were carried out bythe same methods as described in Comparative Example 9 except that thepolymerization time was changed to 20 hours. The results are shown inTable 8.

EXAMPLE 28

A solution of 0.0122 mmol of TiET in toluene was dropwise added to asolution of 12.2 mmol of methylaluminoxane in toluene (supplied byTosoh-Akzo Co.), and the mixture was maintained at +25° C. for one hourto effect aging. Using the thus-aged catalyst, polymerization ofbutadiene was carried out by the same procedures as described in Example26 except that the polymerization time was changed to 19 hours. Theresults are shown in Table 8.

COMPARATIVE EXAMPLE 11

A solution of 0.0122 mmol of TiET in toluene was dropwise added to asolution of 12.2 mmol of methylaluminoxane in toluene (supplied byTosoh-Akzo Co.), and the mixture was maintained at +25° C. for 24 hoursto effect aging. Using the thus-aged catalyst, polymerization ofbutadiene was carried out by the same procedures as described in Example26 except that the polymerization time was changed to 21 hours. Theresults are shown in Table 8.

COMPARATIVE EXAMPLE 12

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 52.4 g of toluene and 5.5 g of butadiene in anitrogen atmosphere, and the content was maintained at +25° C. Into thisglass ampoule, a solution of 12.2 mmol of methylaluminoxane in toluene(supplied by Tosoh-Akzo Co.) and a solution of 0.0122 mmol of TiET intoluene were added in this order to carried out polymerization at +25°C. for 19 hours. The results are shown in Table 8.

TABLE 8 Example No. 26 27 C9 C10* 28 C11* C12* Catalyst TiET TiET TiETTiET TiET TiET TiET Aging [Temp. (° C.) × −25 × −25 × — — +25 × +25 × —Time (h)] 1 1 — — 1 24 — Function (h) 1,000 1,000 — — 10 10 — Polymn.temp. (° C.) +25 +25 +25 +25 +25 +25 +25 BD/Ti*1 (g/mmol) 500 500 500500 500 500 500 Polymn. time (h) 4 20 4 20 19 21 19 Yield (%) 37 60 1222 39 ˜0 18 Polymn. activity 41 14 14 5 9 ˜0 4 Cis content (%) 97 97 9696 96 — 96 10⁻⁴ Mn 35 38 36 38 59 — 49 E.I. (%) 53 79 17 30 33 ˜0 18Mw/Mn 1.92 2.13 2.04 2.36 2.01 — 2.25 *C10, C11 and C12: ComparativeExamples 10, 11 and 12 Function: Value for 6000 exp (−0.0921T) BD/Ti*:Amount of butadiene monomer (g) per mmol of titanium in catalyst

EXAMPLE 29 AND COMPARATIVE EXAMPLES 13-15

Using TiES as a transition metal compound, polymerization of butadienewas carried out under the conditions shown in Table 9 by the sameprocedures as described in Example 26. The results are shown in Table 9.E.I. of polymers obtained in Examples 7 and 9 is also shown in Table 9.

TABLE 9 Example No. 29 7 9 C13* C14* C15* Catalyst TiES TiES TiES TiESTiES TiES Aging −25 × 1 −25 × 1 −25 × 1 — — — [Temp. — — — (° C.) × Time(h)] Function* 1,000 1,000 1,000 — — — (h) Polymn. +25 0 −25 +25 0 −25Temp. (° C.) BD/Ti* 500 500 500 500 500 500 (g/mmol) Polymn. 1.5 0.080.33 17 7 7 time (h) Yield (%) 75 28 38 61 ˜0 ˜0 Polymn. 230 1,600 52016 ˜0 ˜0 activity Cis 92 93 93 87 — — content (%) 10⁻⁴ Mn 129 91 105 81— — E.I. (%) 29 15 18 43 ˜0 ˜0 Mw/Mn 1.91 1.41 1.37 2.21 — — *C13, C14and C15: Comparative Examples 13, 14 and 15 Function: Value for 6000 exp(−0.0921 T) BD/Ti: Amount of butadiene (g) per mmol of titanium incatalyst

EXAMPLE 30 AND COMPARATIVE EXAMPLES 16

Using TiES as a transition metal compound, polymerization of butadienewas carried out under the conditions shown in Table 10 by the sameprocedures as described in Example 26. The results are shown in Table10. E.I. of polymers obtained in Examples 3 and 5 is also shown in Table10.

TABLE 10 Example No. 30 3 2 5 C16* Catalyst TiES TiES TiES TiES TiESAging +25 × +25 × +25 × +25 × +25 × [Temp. 5 m 5 m 5 m 5 m 18 h (° C.) ×Time (min or h)] Function* (h) 10 10 10 10 10 Polymn. Temp. +25 −25 −25−25 −25 (° C.) BD/Ti* 500 500 250 100 500 (g/mmol) Polymn. 1.0 0.05 0.050.05 7.0 time (h) Yield (%) 100 37 100 100 0 Polymn. 450 3,500 4,7001,900 0 activity Cis 92 92 92 92 — content (%) 10⁻⁴ Mn 54 42 38 19 —E.I. (%) 93 44 66 54 0 Mw/Mn 3.07 1.13 1.21 1.17 — *C16: ComparativeExample 16 Function: Value for 6000 exp (−0.0921 T) BD/Ti: Amount ofbutadiene (g) per mmol of titanium in catalyst

EXAMPLES 31-40

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 26.0 g of toluene and a solution of 6.7 mmol ofmethylaluminoxane in toluene (supplied by Tosoh-Akzo Co.). The ampoulewas maintained at an aging temperature shown in Tables 11 and 12, and asolution of 0.0067 mmol of TiES in toluene was dropwise added into theampoule, and the content was maintained for an aging time shown inTables 11 and 12. Then the content was cooled to −25° C., and a solutionof 2.0 g of butadiene in 6.0 of toluene was added to carry outpolymerization at that temperature for 30 minutes. Thereafterafter-treatments were carried out by the same procedures as described inExample 26. The results are shown in Tables 11 and 12.

TABLE 11 Example No. 31 32 33 34 35 Catalyst TiES TiES TiES TiES TiESAging [Temp. +50 × 1 +50 × 20 +25 × 1 +25 × 20 +25 × 60 (° C.) × Time(min)] Function* (h) 1 1 10 10 10 Polymn. −25 −25 −25 −25 −25 Temp. (°C.) BD/Ti* 300 300 300 300 300 (g/mmol) Polymn. 0.5 0.5 0.5 0.5 0.5 time(h) Yield (%) 81 50 98 93 80 Polymn. 480 300 590 560 480 activity Ciscontent 92 92 92 92 92 (%) 10⁻⁴ Mn 79 147 42 48 64 E.I. (%) 31 10 70 5938 Mw/Mn 1.49 1.5 1.76 1.47 1.48

TABLE 12 Example No. 36 37 38 39 40 Catalyst TiES TiES TiES TiES TiESAging +25 × 0 × 0 × −25 × −25 × [Temp. (° C.) × 3 h 10 m 3 h 10 m 5 hTime (min or h)] Function* (h) 10 100 100 1,000 1,000 Polymn. −25 −25−25 −25 −25 Temp. (° C.) BD/Ti* 300 300 300 300 300 (g/mmol) Polymn. 0.50.5 0.5 0.5 0.5 time (h) Yield (%) 11 88 81 51 87 Polymn. 66 530 480 300300 activity Cis 92 92 92 92 92 content (%) 10⁻⁴ Mn 89 50 32 71 45 E.I.(%) 4 53 77 21 59 Mw/Mn 1.70 1.45 1.65 1.40 1.31 *Function: Value for6000 exp (−0.0921 T) BD/Ti: Amount of butadiene (g) per mmol of titaniumin catalyst

EXAMPLES 41 AND 42

Using TiTMS as transition metal compound, polymerization of butadienewas carried out by the same procedures as described in Example 26. Thepolymerization conditions and results are shown in Table 13.

COMPARATIVE EXAMPLE 17 AND EXAMPLE 43

Using TiTMS as transition metal compound, polymerization of butadienewas carried out by the same procedures as described in ComparativeExample 9. The polymerization conditions and results are shown in Table13.

TABLE 13 Example No. 41 C17* 42 43 Catalyst TiTMS TiTMS TiTMS TiTMSAging [Temp. (° C.) × +25 × 5 — +25 × 5 — Time (min)] — — Function* (h)10 — 10 — Polymn. Temp. (° C.) +25 +25 −25 −25 BD/Ti* (g/mmol) 100 100100 100 Polymn. time 15 m 25 m 1 h 1 h (min or h) Yield (%) 97 85 94 34Polymn. activity 390 200 94 34 Cis content (%) 88 88 92 92 10⁻⁴ Mn 13 2724 42 E.I. (%) 73 31 40 8 Mw/Mn 1.82 1.81 1.12 1.14 *C17: ComparativeExample 17 Function: Value for 6000 exp (−0.0921 T) BD/Ti: Amount ofbutadiene (g) per mmol of titanium in catalyst

COMPARATIVE EXAMPLE 18

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 49 g of toluene and 1.0 g of butadiene in anitrogen atmosphere, and the content was maintained at a constanttemperature of 50° C. Then a solution of 0.02 mmol of n-butyllithium inhexane was added to carry out polymerization at 50° C. for 120 minutes.To this polymerization solution, a solution of 0.1 mmol of4,4′-bisdiethylaminobenzophenone (hereinafter abbreviated to “EAB”) intoluene was added, and the mixture was maintained at 50° C. for 6 hoursto effect a terminal modification reaction. Then a small amount of anaqueous acidic methanol was added to terminate the terminal modificationreaction, and the polymerization liquid was poured into a salient amountof an aqueous acidic methanol containing an antioxidant to precipitate apolymer. The polymer was dried and weighted to determine the yield ofpolymer. The yield and results of the following analysis of polymer areshown in Table 14.

The microstructure of the polymer was determined by NMR analysis in amanner similar to that in the preceding working examples. GPC analysiswas conducted by using an ultraviolet absorption detector (UV, detectingwavelength 310 nm) and a differential refractometer (RI) as detector,two connected columns GMH, or connected G-7000 and G-5000 (both suppliedby Tosoh Corp.) as column, and THF as eluting liquid. The number averagemolecular weight (Mn) and the molecular weight distribution (Mw/Mn) weredetermined according to a calibration curve drawn by using standardpolybutadiene (supplied by Polymer Laboratories Co.). The degree ofterminal modification was determined by the following formula:

(UV peak intensity/RI peak intensity)×10⁻⁴ Mn

COMPARATIVE EXAMPLE 19

By the method described in Example 1 of WO 95/04090, butadiene waspolymerized at 60° C. in cyclohexane by using neodymiumoctenate/dibuthylaluminum hydride/tributylphosphine/diethylaluminumchloride as polymerization catalyst, and then the polymerizationsolution was treated with EAB to effect terminal modification reactionat 60° C. for 70 minutes. The thus-obtained polymer was recovered andanalyzed by the same procedures as employed in Comparative Example 18.The results are shown in Table 14. The molecular weight distributionMw/Mn of the polymer as determined by GPC-MALLS method was 2.3.

EXAMPLE 44

A solution of 0.05 mmol of TiES in toluene was dropwise added to asolution of 50 mmol of methylaluminoxane, and the mixture was maintainedat 25° C. for 5 minutes to effect aging.

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 49 g of toluene and 1.0 g of butadiene in anitrogen atmosphere, and the content was cooled to −25° C. Theabove-mentioned aged catalyst was added into the ampoule to carry outpolymerization at −25° C. for 5 minutes. Then a solution of 5 mmol ofEAB in toluene was added to the polymer solution and, while thetemperature of the polymer solution was allowed to naturally rise toroom temperature, a terminal modification reaction was carried out for60 minutes. Thereafter an aqueous acidic methanol was added to terminatethe terminal modification reaction, and the polymerization solution waspoured into a salient amount of an aqueous acidic methanol containing anantioxidant to precipitate a polymer. The polymer was dissolved intoluene, and the polymer solution was subjected to centrifugalseparation to remove the ash content, and then a polymer wasreprecipitated from an aqueous acidic methanol. The thus-obtainedpolymer was dried and weighed to determine yield of the polymer.

The polymer was analyzed by the same procedures as employed inComparative Example 18. The results are shown in Table 14. As seen fromTable 14, the butadiene polymer had a high cis-bond content, a narrowmolecular weight distribution and a terminal modification degree of 86%.This polymer was obtained with an improved efficiency.

EXAMPLE 45

By the same procedures as employed in Example 44, polymerization ofbutadiene, terminal modification, recovery and analysis of polymer werecarried out except that amount of methylaluminoxane was changed to 100mmol, amount of TiES was changed to 0.1 mmol, and 100 mmol of phenylisocyanate as terminal modifier was used. Low molecular weightimpurities such as unreacted phenyl isocyanate were completely removedby GPC from the thus-obtained polymer, and thereafter the polymer wassubjected to ¹H-NMR analysis under the following conditions. Solvent:heavy methylene chloride, internal standard: tetramethylsilane,temperature: 30° C., pulse delay: 3.362 seconds, integrated number:11,526. From signal intensity of unsaturated proton derived frombutadiene units and siganal intensity of phenyl proton, which occur inthe ¹H-NMR spectrum, the molar ratio of butadiene unit to phenyl groupwas calculated as 695/1. The number average molecular weight (Mn) ofpolymer as determined by GPC measurement was 38,600. Thus, the terminalmodification degree of polymer was calculated as 100%. The results ofanalysis are shown in Table 14.

TABLE 14 Example No. 44 45 C18* C19* Catalyst TiES TiES n-BuLi* Nd*Aging [Temp. (° C.) × +25 × 5 +25 × 5 — — Time (min)] — — BD/Ti*(g/mmol) 20 10 — — BD/Li* (g/mmol) — — 50 — Polymn. temp. (° C.) −25 −25+50 +60 Polymn. time 5 m 5 m 2 h 30 m (min or h) Yield (%) 100 100 10041 Cis content (%) 93 93 35 97 10⁻⁴ Mn 7.8 3.9 6.4 6.0 Mw/Mn 1.21 1.351.11 3.1 UV/RI 0.65 0.92 0.73 10⁻⁴ Mn × UV/RI 5.07 5.89 4.36 Term. mod.deg. (%)* 86 100 100 74 *C18 and C19: Comparative Examples 18 and 19n-BuLi: n-butyllithium catalyst Nd: neodymium-containing catalyst BD/Ti:Amount of butadiene (g) per mmol of titanium in catalyst BD/Li: Amountof butadiene (g) per mmol of lithium in catalyst

Butadiene polymer obtained by polymerization at −25° C. using TiEScatalyst in Example 2 was regarded as being substantially free frombranched structure. Thus, polymers obtained in Examples 44 and 45 arepresumed to be substantially free from a branched structure.

COMPARATIVE EXAMPLE 20

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 49 g of toluene and 1.0 g of butadiene in anitrogen atmosphere, and the content was maintained at a constanttemperature of 50° C. Then a solution of 0.0014 mmol of tintetrachloride in toluene was added to carry out polymerization at 50° C.for 60 minutes. To this polymerization solution, a minor amount ofmethanol was added to be quenched, and the polymerization solution waspoured into a salient amount of methanol containing an antioxidant toprecipitate a polymer. The polymer was dried and weighted to determinethe yield of polymer. The yield and results of the analysis of polymerare shown in Table 15.

EXAMPLE 46

A solution of 0.033 mmol of TiES in toluene was dropwise added to asolution of 33.3 mmol of methylaluminoxane, and the mixture wasmaintained at 25° C. for 5 minutes to effect aging.

A sealable pressure-resistant glass ampoule having an inner volume of150 ml was charged with 49 g of toluene and 1.0 g of butadiene in anitrogen atmosphere, and the content was cooled to −25° C. Theabove-mentioned aged catalyst was added into the ampoule to carry outpolymerization at −25° C. for 5 minutes. A minor amount of thepolymerization solution was sampled for GPC measurement. Then a solutionof 0.013 mmol of tin tetrachloride in toluene was added to carry outpolymerization for 60 minutes while the temperature was allowed tonaturally rise to room temperature. To this polymerization solution, aminor amount of methanol was added to be quenched, and thepolymerization solution was poured into a salient amount of an aqueousacidic methanol containing an antioxidant to precipitate a polymer. Thepolymer was dissolved in toluene and then the polymer solution wassubjected to centrifugal separation to remove the ash content. Thepolymer was then re-precipitated from an aqueos methanol, and dried andweighted to determine the yield of polymer. The results are shown inTable 15. As seen from Table 15, the thus-obtained butadiene polymercomposition had a high cis-bond content, uncoupled polymer (I) in thepolymer composition had a narrow molecular weight distribution, and thedegree of coupling was 36%. This polymer composition was obtained withan improved efficiency.

EXAMPLE 47

By the same procedures as employed in Example 46, polymerization ofbutadiene and analysis of polymer were carried out except that amount ofmethylaluminoxane was changed to 50 mmol, amount of TiES was changed to0.05 mmol, and 0.04 mmol of ethyl acetate was used instead of tintetrachloride as a coupling agent. The results are shown in Table 15.

TABLE 15 Example No. C20* 46 47 Catalyst n-BuLi* TiES TiES Aging [Temp.(° C.) × — +25 × 5 +25 × 5 Time (min)] BD/Ti* (g/mmol) — 30 20 BD/Li*(g/mmol) 50 — — Polymn. +50 −25 −25 temp. (° C.) Polymn. time 1 h 5 m 5m (min or h) Coupling agent SnCl₄ SnCl₄ CH₃COOEt Yield (%) 100 100 100Cis content (%) 35 93 93 Polymer (I), 10⁻⁴ Mn 7.0 6.7 5.3 Polymer (I),Mw/Mn 1.08 1.26 1.21 Polymer (II), 20.0 28.3 15.6 10⁻⁴ Mw/Mn Polymer(II), Mw/Mn 1.12 1.28 1.03 Coupling degree 35 36 17 *C20: ComparativeExample 20 n-BuLi: n-butyllithium catalyst BD/Ti: Amount of butadiene(g) per mmol of titanium in catalyst BD/Li: Amount of butadiene (g) permmol of lithium in catalyst

From the results of GPC-MALLS measurement shown in Example 2 andComparative Examples 1 and 2 in Table 1, it is confirmed that abutadiene polymer obtained by polymerization using TiES catalyst issubstantially free from a branched structure. Thus, polymers (I) in thepolymer compositions obtained in Examples 46 and 47 are presumed to besubstantially free from a branched structure.

INDUSTRIAL APPLICABILITY

In the process for production of a conjugated diene polymer according tothe present invention, a living polymerization reaction proceeds with ahigh activity. Therefore, the butadiene polymer of the presentinvention, which is produced by this process, is characterized as havinga high living polymer chain content, a high cis-bond content, a highmolecular weight, a narrow molecular weight distribution, and anextremely reduced content of branched structure. Due to thesecharacteristics, terminal-modified butadiene polymer made from thebutadiene polymer, and a coupled butadiene polymer made therefrom havespecific chemical structures, and thus, these butadiene polymers areexpected to have enhanced utility as novel rubber materials in variousfields.

What is claimed is:
 1. A butadiene polymer which is a homopolymer ofbutadiene or a copolymer of butadiene with a monomer copolymerizabletherewith, comprising at least 50% by weight of butadiene units in thebutadiene polymer, wherein the content of butadiene units having acis-bond in the total butadiene units is at least 50%, wherein thenumber average molecular weight (Mn) of the butadiene polymer is in therange of 1,000 to 10,000,000, wherein the ratio (Mw/Mn) of the weightaverage molecular weight (Mw) to the number average molecular weight(Mn) of the butadiene polymer is below 1.5, and wherein the butadienepolymer has at least 80%, based on the total molecular chains, of livingchains containing a transition metal of group IV of the periodic tableat a terminal thereof.
 2. A process for producing a conjugated dienepolymer, comprising polymerizing a conjugated diene monomer alone, or atleast 50% by weight of a conjugated diene monomer with not more than 50%by weight of a monomer copolymerizable therewith at a temperature of nothigher than 10° C. in the presence of a catalyst comprising (A) acompound of a transition metal of group IV of the periodic table havinga cyclopentadienyl structural unit which may have a substituent, and (B)at least one co-catalyst selected from (a) an organoaluminum-oxycompound, (b) an ionic compound capable of reacting with the transitionmetal compound (A) to give a cationic transition metal compound, (c) aLewis acid compound capable of reacting with the transition metalcompound (A) to give a cationic transition metal compound, and (d) anorganometallic compound having a main element metal of groups I to IIIof the periodic table, wherein said transition metal compound (A) is orhas been contacted with said co-catalyst under conditions satisfying thefollowing formulae (α) and (β): −100<T<80  (α)0.017<t<6000×exp(−0.0921×T)  (β) wherein t is contact time (minutes) andT is contact temperature (°C.).
 3. The process for producing aconjugated diene polymer according to claim 2, wherein said compound (A)of a transition metal of group IV of the periodic table having acyclopentadienyl structural unit has a substituent having at least onekind of an atomic group selected from the group consisting of a carbonylgroup, a sulfonyl group, an ether group and a thioether group.
 4. Theprocess for producing a conjugated diene polymer according to claim 2,wherein said compound (A) of a transition metal of group IV of theperiodic table having a cyclopentadienyl structural unit having asubstituent with at least one kind of an atomic group selected from thegroup consisting of a carbonyl group, a sulfonyl group, an ether groupand a thioether group is a transition metal compound of group IV of theperiodic table represented by the following formula (4) or formula (5):

wherein M is a transition metal of group IV of the periodic table, X¹,X² and X³ are hydrogen, a halogen, a C1-12 hydrocarbon group or a C1-12hydrocarbon-oxy group, Y¹ is hydrogen or a C1-20 hydrocarbon group whichmay form a ring together with the cyclopentadienyl group, Z¹ and Z² arehydrogen or a C1-12 hydrocarbon group, A is oxygen or sulfur, R¹ ishydrogen, a C1-12 hydrocarbon group, a C1-12 hydrocarbon-oxy group or aC1-12 hydrocarbon-thio group, and n is an integer of 0 to 5, and thepentagon with a circle therein represents a cyclopentadienyl ringstructure,

wherein M is a transition metal of group IV of the periodic table, X¹,X² and X³ are hydrogen, a halogen, a C1-12 hydrocarbon group or a C1-12hydrocarbon-oxy group, Y¹ is hydrogen or a C1-20 hydrocarbon group whichmay form a ring together with the cyclopentadienyl group, Z¹ and Z² arehydrogen or a C1-12 hydrocarbon group, A is oxygen or sulfur, R² is aC1-12 hydrocarbon group, n is an integer of 0 to 5, and the pentagonwith a circle therein represents a cyclopentadienyl ring structure.
 5. Aterminal-modified butadiene polymer which is a homopolymer of butadieneor a copolymer of butadiene with a monomer copolymerizable therewith,having at least 50% by weight of butadiene units, wherein the content ofbutadiene units having a cis bond in the total butadiene units of thebutadiene polymer is at least 50%; the number average molecular weight(Mn) of the butadiene polymer is in the range of 1,000 to 10,000,000;the ratio (Mw/Mn) of the weight average molecular weight (Mw) to thenumber average molecular weight (Mn) of the butadiene polymer is smallerthan 3.0; a relationship represented by the formula;log(Mw/Mn)<0.162×log(Mw)−0.682 is satisfied between the weight averagemolecular weight (Mw) and the ratio (Mw/Mn); and the butadiene polymerhas at least 10%, based on the total polymer chains, of polymer chainshaving a functional group at a terminal thereof.
 6. A process forproducing a terminal-modified conjugated diene polymer, comprising thesteps of: polymerizing a conjugated diene monomer alone, or at least 50%by weight of a conjugated diene monomer with not more than 50% of amonomer copolymerizable therewith in the presence of a catalystcomprising (A) a compound of a transition metal of group IV of theperiodic table having a cyclopentadienyl structural unit, and (B) atleast one co-catalyst selected from (a) an organoalumimun-oxy compound,(b) an ionic compound capable of reacting with the transition metalcompound (A) to give a cationic transition metal compound, (c) a Lewisacid compound capable of reacting with the transition metal compound (A)to give a cationic transition metal compound, and (d) an organometalliccompound having a main element metal of groups I to III of the periodictable, wherein said transition metal compound (A) is or has beencontacted with said co-catalyst under conditions satisfying thefollowing formulae (α) and (β): −100<T<80  (α)0.017<t<6000×exp(−0.0921×T)  (β) wherein t is contact time (minutes) andT is contact temperature (°C.); and then, contacting the thus-producedconjugated diene polymer with a reagent capable of reacting with aliving polymer having a transition metal of group IV of the periodictable at a terminal thereof.
 7. A coupled butadiene polymer compositioncomprising: (I) 0 to 90 parts by weight of a polymer which is ahomopolymer of butadiene or a copolymer of butadiene with a monomercopolymerizable therewith, and which has at least 50% by weight ofbutadiene units, and in which the content of butadiene units having acis bond in the total butadiene units is at least 50%, the numberaverage molecular weight (Mn) is in the range of 1,000 to 10,000,000,and a relationship represented by the formula:log(Mw/Mn)<0.162×log(Mw)−0.682  is satisfied between the weight averagemolecular weight (Mw) and the ratio (Mw/Mn); and (II) 100 to 10 parts byweight of a polymer composed of at least two molecules of theabove-mentioned polymer (I), bonded through a coupling agent.
 8. Aprocess for producing a coupled conjugated diene polymer, comprising thesteps of: polymerizing a conjugated diene monomer alone, or at least 50%by weight of a conjugated diene monomer with not more than 50% by weightof a monomer copolymerizable therewith in the presence of a catalystcomprising (A) a compound of a transition metal of group IV of theperiodic table having a cyclopentadienyl structural unit, and (B) atleast one co-catalyst selected from (a) an organoalumimun-oxycompound,(b) an ionic compound capable of reacting with the transition metalcompound (A) to give a cationic transition metal compound, (c) a Lewisacid compound capable of reacting with the transition metal compound (A)to give a cationic transition metal compound, and (d) an organometalliccompound having a main element metal of groups I to III of the periodictable, wherein said transition metal compound (A) is or has beencontacted with said co-catalyst under conditions satisfying thefollowing formulae (α) and (β): −100<T<80  (α)0.017<t<6000×exp(−0.0921×T)  (β) wherein t is contact time (minutes) andT is contact temperature (°C.); and then, contacting the thus-producedconjugated diene polymer with a coupling agent capable of reacting witha living polymer having a transition metal of group IV of the periodictable at a terminal thereof.